home Thyroid A message on the topic of hormones. The chemistry of love is a disease, hormones, pheromones, scientific research. Is it possible to make a love potion? Or a medicine to stop loving? How long does the feeling of falling in love last?

A message on the topic of hormones. The chemistry of love is a disease, hormones, pheromones, scientific research. Is it possible to make a love potion? Or a medicine to stop loving? How long does the feeling of falling in love last?

The thyroid gland is an organ of the endocrine system, which quite often undergoes malignant degeneration. About 1% of all cancers are thyroid cancer, being the most common tumor among endocrine organs.

It is twice as common in women as in men. The concept of this cancer was first voiced at the end of the 18th century, and the microscopic picture of the pathology was described by Libert in 1862. Initial research in the field of diagnosis and treatment was carried out at the end of the 19th century. And the real revolution was the successful surgical intervention performed by the Russian surgeon Subbotin in 1893.

Unfortunately, even now there is no highly accurate method for diagnosing cancer. The answer to the question “how to treat thyroid cancer” depends on many factors: the duration of the process, the age of the patient and the structure of the tumor itself. Let us consider in detail information about the causes, methods of recognizing the disease and a way out of the current situation.

Multifaceted causes

There are many myths surrounding malignant degeneration of the thyroid gland. Let's try to show them in a different light for the sake of clarity of the present picture.

Follicular cancer is more common in people suffering from iodine deficiency, and papillary cancer is more common in those who receive the required amount of iodine. But the deficiency of this microelement is not the only reliable reason for the appearance of a neoplasm. The direct connection between the patient’s residence in an area of iodine deficiency and the development of thyroid cancer is relative, since the colossal role of radioactive radiation in the appearance of a malignant tumor has been proven.

Until recently, it was believed that nodular goiter was an excellent breeding ground for malignant degeneration. In fact, only some types of nodes are prone to becoming malignant, but sometimes cancer affects healthy, unchanged gland tissue.

The predecessors of this terrible pathology and views on causality are a hot topic for discussion among doctors. Moreover, the incidence of thyroid cancer is steadily increasing, and affects mainly young people of working age: over the last decade, the number of the affected population has increased by 5%. Research conducted in the field of studying the disease has shown a gradation of causes by importance and clearly proven things.

So, the main causes and risk factors for thyroid cancer are:

radioactive irradiation of the tonsils, thyroid and parathyroid glands in children and adolescents;
endemic area - lack of iodine in soil, air, water;
neck injuries;
chronic inflammatory and dystrophic lesions of the thyroid gland;
genetic predisposition.

This is interesting! Hereditary cancer (caused by a genetic mutation) appears at 30 years of age, radiation-induced or spontaneous (as a result of the influence of various factors) - at 40-45 years of age. However, their clinical course does not differ.

Increased excitability of the nervous system (stressful situations).
Goiter with normal or reduced thyroid function (including artificially created by long-term use of thyreostatics (mercazolin)).
Young women (under 40 years of age).

It is important to know! Although hormonal changes during pregnancy and breastfeeding are physiological, they often provoke the development of malignant neoplasms of the thyroid gland.

Cancer classification: a terrifying kaleidoscope

Histologists evaluate the tumor not only externally, but also study its internal features. The neoplasm has its own morphology, i.e. Under a microscope, the structure of each type is different. Differentiation (from English - different, various) - the ability to recognize one or another type. Undifferentiated cancer is an irregularly shaped cell collected in a conglomerate and difficult to identify.

Differentiated - a specific morphological picture allows you to determine the exact type of cancer:

papillary
follicular

Undifferentiated - giant and small cell, anaplastic.
Poorly or difficultly differentiated – medullary.
Other types of cancer: mucous, mixed medullary and follicular cell, squamous cell.

This is interesting! In 70-80% of thyroid cancer pathology, papillary cancer occurs, follicular - 10%, mixed - 20%, anaplastic - 0.5-1%.

Table 1: According to the clinical course, cancer is divided into 4 stages:

Process stage	Tumor size	Location	Metastases	Relation to the thyroid capsule	Mobility
1	Small	In one lobe of the thyroid gland	None	Inside the capsule	Saved
2	Half of the thyroid gland		Into the cervical lymph nodes on one side.	Sprouts capsule	Saved
3	More than a half		Into the cervical lymph nodes on both sides, into the mediastinal lymph nodes.	Outside	Limited in mobility due to germination into neighboring organs
4	The entire area of the thyroid gland		Into neighboring organs, bones, lungs.	Outside	motionless

This is interesting! Regional metastasis is the spread of metastases to the nearest cervical lymph nodes, and distant metastases to organs. The latter, as a rule, occur when the tumor diameter is more than 3 cm, more often in children under 12 years of age, compared to adults.

Cancer clinic: the beast sneaks up unnoticed

The insidiousness of the tumor lies in the fact that it develops unnoticed by the patient, or the clinical signs are misleading with their nonspecificity and diversity, which forces them to seek help from highly specialized specialists - an ENT specialist, a surgeon, a therapist.

Without knowing the specifics and unpredictability of thyroid cancer, doctors confuse it with other diseases, and precious time is lost to treat the hidden disease. In order to suspect an illness, you need to carefully examine the neck area and ask the patient about complaints and the subtleties of their development.

Progression of symptoms: the further into the forest, the more firewood

The main symptom that worries 50-60% of patients is the appearance of a tumor in the thyroid area. When the cancer progresses and grows into neighboring organs, the severity of the patient’s condition worsens: general weakness appears, the temperature rises without objective reasons.

Diarrhea occurs in 60% of patients with medullary cancer due to the fact that the hormonally active tumor produces prostaglandins and other biological substances, which increase intestinal contractions. Depending on which organ is involved in the process, the clinic becomes peculiar and alarming.

Table 2: The spectrum of manifestations of thyroid cancer depending on the organ involved in the process:

Affected organ	Patient complaints
Pharynx and larynx	Sore throat, choking, feeling of pressure and the presence of a foreign body during swallowing and talking.
Esophagus	The impossibility and paradox of swallowing: solid food passes more easily than liquid food.
Bronchi	Paroxysmal dry or wet cough with discharge of pus, pain in the chest, shortness of breath, high fever.
Sympathetic nervous system	Disturbance of the innervation of the eye muscles is characterized by a triad of symptoms: constriction of the pupil, drooping of the upper eyelid, and retraction of the eyeball. Vasodilation of the affected half of the face and excessive sweating are possible.

It is important to know! A tumor that grows into the bronchi and blocks their lumen simulates bronchitis. This form of cancer is called pseudoinflammatory.

History taking

During the survey, there are some key points to find out:

When did the patient first discover the tumor?
What is its growth rate?
Symmetry and size from the beginning to the time of seeking medical help.
Are there any cases of cancer in your relatives?

Inspection

Visual assessment and palpation of the neck area provides some data:

the malignant tumor is asymmetrical, irregular in shape;
densely elastic, lumpy;
limited in mobility;
sizes from medium to large (small ones cannot be detected without additional diagnostic methods);
a network of venous vessels on the surface of the chest, if the tumor metastasizes into the superior vena cava;
in case of metastasis, the nearest lymph nodes are enlarged, dense, fused with soft tissues, sometimes with each other.

It is important to know! The lumpy surface of the thyroid gland is also characteristic of tuberculosis, a rare disease of this endocrine organ. The benefit of the latter pathology is evidenced by a positive Mantoux test, a history of tuberculosis, and contact with an infectious patient.

The video in this article clearly and briefly describes the most common symptoms and external manifestations of cancer, which should lead the patient to suspect he has this disease and immediately consult a doctor.

TAB is the gold standard for diagnosis

Fine-needle aspiration biopsy - intravital tissue removal with further examination under a microscope. There are 2 options for the procedure: preoperative and emergency (performed during surgery to quickly clarify the malignancy of the process and determine the scope of the operation).

It is FNA that makes it possible to study multifocality - individual very small zones of tumor growth, which cannot be seen during ultrasound and visually during surgery. Since papillary and follicular cancer are more common, they are distinguished by their structural and developmental features.

Table 3: Comparative characteristics of differential cancer types:

	Papillary	Follicular
Capsule	Absent	Present
Hormonal activity	Not inherent	Characteristic
Path of spread of metastases	Hematogenous (with blood flow or by blockage of blood vessels).	Lymphogenic (via lymphatic ducts).
Typical structure	Papillary formations in the form of branches, with a rich vascular network; ovoid cells with transparent nuclei and inclusions inside.	Small bubbles (follicles) of different shapes and sizes with tubular formations inside, as well as with a viscous (thick) substance.
Tumor color on section	Brown-purple	Gray or pink
Special Feature	Dense, woody, adjacent to the trachea, less than 1 cm.	Smooth, more than 1.5 cm in diameter.

Undifferentiated cancer spreads its cells (metastases) in two ways - with blood and lymph.

This is interesting! Experiments have proven that freely circulating cancer cells are less dangerous due to their destruction by the body's protective proteins than those that disrupt the patency of blood vessels (so-called emboli).

Under a microscope, giant cell carcinoma looks like elongated, huge cells with several nuclei. Metastases and the cells themselves are hormonally inactive. Small cell – multiple, small, chaotically glued cells together.

Ultrasound examination (ultrasound)

A quick and relatively informative method allows you to evaluate tumor data:

A cancerous tumor has characteristic features:

irregular shape with “poor” blood supply;
not symmetrical;
does not have a capsule and clear contours;
reflects ultrasound poorly.

This is interesting! The echographic parameters of the thyroid gland exceed its real ones by 10%.

CT scan

Image of the organ on a computer and on film in the form of sections of a certain thickness - from a fraction of a mm to several mm, which depends on the quality of the device. The thinner the ball, the more valuable the research method becomes, and the more accurate the diagnosis.

Scintigraphic examination (SGI) - radioisotope method

The method involves introducing into the vessels a radioactive contrast agent (technetium, thallium, iodine 123 or 133), capable of reflecting light, and monitoring its accumulation in certain places. Most often, malignant nodes are “cold”, i.e. not prone to absorb chemicals. Benign ones, on the contrary, are “hot”.

The advantage of this method is that the required dose of diagnosticum is not toxic to the body. One type of scintigraphy - biphasic scintigraphy of the neck in several projections - is an addition to the main study.

Main indications:

uncertain morphological picture (especially for follicular cancer);
assessment of the condition of the capsule.

The purpose of the study is to study the following parameters:

localization (placement) of the tumor;
size;
relation to adjacent tissues;
functional activity (possibility of radionuclide accumulation).

This is interesting! A highly accurate method for distinguishing between cancer and benign processes is quantitative scintigraphy labeled with the amino acid methionine. The principle of manipulation is that adenoma does not absorb the medicine well 3 hours after administration, but cancer does, on the contrary, well.

Thyroid lymphography

Examination of the thyroid gland and nearby lymph nodes and ducts after contrast administration.

Defects in filling the lobes of an organ with contrast indicate partial damage, and if the contrast does not spread, total damage (“silent” thyroid gland). Such changes affect both lymph nodes and lymphatic ducts if metastases damage them.

Rheothyroidography

Study of blood flow speed, functionality of thyroid vessels, their patency. With a malignant lesion, the vascular pattern becomes spear-shaped, the intensity of blood flow decreases (displayed graphically by a curved line).

Thermothyroidography

Measuring the temperature of individual areas of the thyroid gland and transmitting the image to the device monitor. Individual regions are colored from cold to hot shades, which makes it possible to judge the localization of pathological foci.

Radioimmunoassay (RIA)

The laboratory method is based on the binding of a radiation-labeled substance to an immunological complex. Invented for the quantitative study of thyroid-specific tumor markers: thyroglobulin in differentiated types of cancer, calcitonin in poorly differentiated types.

The material required for the study is the washout from the puncture needle that was used to perform FNA. The main goal is to determine metastases in the lymph nodes.

Molecular research

Biological study of the genetic apparatus for the presence of mutations or anomalies. It is advisable to perform this if there is a burdened family history - blood relatives with cancer.

General blood analysis

There are no signs of inflammation; ESR increases only with late detected cancer. Has no informational value.

Conservative treatment: diplomatic negotiations with oncology and chances of recovery

Conservative therapy is an alternative approach to solving the problem without surgery. There are few fans of the “no-scalpel strategy” among oncologists.

It is believed that after such therapy the size of the tumor decreases mainly due to the elimination of inflammatory components, the general condition of the patient improves and a false impression is created about his recovery. In fact, as a result of delayed radical surgery, the tumor most often develops gradually.

What evidence supports gentle treatment?

The effects of iodides, hormones, and rays are indicated only in the initial stage of the process under close monitoring of tumor progression, or as an addition to surgery in the case of an advanced malignant process. Conservative treatment is considered as an option if it is impossible to surgically solve the problem in elderly people, as well as in all people for a short period of time, with consideration of the prospect of immediate removal of part and all of the thyroid gland.

Use of hormonal drugs

Levothyroxine is the drug of choice most often.

Suppressive hormone therapy relies on the use of high doses of the drug - 2-3 mcg/kg/day. In this case, the level of thyroid-stimulating hormone (TSH) should be within 0.1-0.3 mIU/l. Laboratory control is carried out once every 3 months. But since long-term use of thyroid hormones is fraught with the development of side effects (osteoporosis, hyperthyroidism, arrhythmia), doctors prescribe a different, milder type of treatment.

Hormone replacement therapy - levothyroxine is administered to adults at a dose of 1.6 mcg/kg/day, to children - 1.5-2 mcg/kg/day. TSH reaches a level of 0.5-5 mIU/l.

Instructions for L-thyroxine:

Composition: 1 tablet contains 25, 50, 75, 100, 125, 150, 175 or 200 mcg of levothyroxine.
Pharmacotherapeutic group: thyroid hormones.
Indications:

treatment of benign neoplasms of the thyroid gland;
replacement or suppressive therapy for cancer after removal of the thyroid gland;
hypothyroidism

Directions for use: take the tablet in the morning, on an empty stomach, 30 minutes before meals, chew or drink with water.
Contraindications:

hyperthyroidism (thyrotoxicosis);
acute myocardial infarction;
diabetes mellitus (with caution);
pituitary and adrenal insufficiency.

Drug interactions:

When taking L-thyroxine simultaneously with drugs such as aluminum compounds and other acid-lowering agents, hormonal contraceptives, it is necessary to increase the dose of thyroid hormone.
Glucocorticoids (hormones of the adrenal cortex), the antiarrhythmic drug amiodarone and iodine-containing drugs inhibit the conversion of thyroxine into a more active form of the iodinated hormone - triiodothyronine. Therefore, you should avoid combining L-thyroxine with the above groups of pharmaceuticals.
Products and foods that contain soy inhibit the absorption and assimilation of L-thyroxine in the intestines.

Price: 50 tablets of 50 mcg - about 250-300 rubles.

External beam radiotherapy

External irradiation of the neck and mediastinum. The total absorbing dose and irradiation regimen depend on the location of the tumor, growth rate and degree of proliferation at the moment.

Main indications:

tumor invasion of the trachea, esophagus, and other organs;
undifferentiated cancer.

Telegammatherapy

A more advanced treatment method compared to radiotherapy: gamma rays are harsher, penetrate deeper into the pathological focus, but do not damage the skin and organs of the neck.

Radioiodine therapy

An auxiliary method of radiation therapy, treatment of thyroid cancer with labeled iodine. The technique is painless, and also convenient in that the drug is administered into the body through the mouth in the form of gelatin capsules or solution.

Indications:
performing non-radical surgery;
tumor growth of the capsule;
metastasis to the lateral cervical or upper mediastinal lymph nodes;
childhood and retirement age.

After the operation, radioactive iodine is used to block (ablate) the vessels that supply blood to the remains of the removed thyroid gland in order to prevent relapse.

It is important to know! The use of L-thyroxine and labeled iodine is incomparable, therefore, a few days before the radioiodine therapy procedure, endocrinologists strongly recommend stopping the use of thyroid hormones, as well as iodine-containing products.

Chemotherapy

A course of chemical administration is highly effective for anaplastic and difficult-to-differentiate cancer, but follicular and papillary thyroid cancer does not respond to such treatment. Cytostatic drugs are often used to stop the development of the tumor and promote its death.

Clinical examination

Registration of the patient in specialized medical institutions (oncology or endocrinology dispensary) means periodic examination by a doctor over a period of time.

Once every six months or quarter, the patient undertakes to undergo examinations:

determination of TSH and thyroglobulin levels;
Ultrasound of the thyroid gland;
X-ray or CT scan of the lungs and skeleton.

In this case, the patient receives adequate hormone therapy.

Surgery - at the honorary level

There is still ongoing debate between supporters of conservative and radical treatment of thyroid cancer. The situation is heating up in a “I want it and I’m injecting it” type, especially if we are talking about a young patient.

It is no secret that there is a risk of postoperative disability with mandatory lifelong use of hormones and, accordingly, financial costs for the patient himself and the loss of the country’s working population. Therefore, on the one hand, there is a desire to preserve the organ as much as possible to maintain normal hormonal levels without taking chemical analogues of thyroxine, on the other hand, organ preservation is fraught with aggravation of the disease.

Despite all the pros and cons of each therapeutic aspect, the surgical method of treating thyroid cancer is recognized worldwide as the leading one, and the volume of the operation depends on the morphological form and extent of the process.

Lobectomy with isthmus resection

Removal of one lobe of the thyroid gland along with the isthmus is indicated for follicular cancer with typical invasion of the thyroid capsule and for papillary cancer with a diameter of less than 1 cm without metastases and damage to the capsule.

Total thyroidectomy and central lymph node dissection (CLD)

Removal of the entire thyroid gland with nearby lymph nodes (superior mediastinal, peritracheal) and soft tissues. It is performed during the progression of the malignant process and the presence of metastases.

Supplemented by a course of radiation (cobalt, iodine) or chemical therapy. After surgery, the patient takes levothyroxine for life as replacement therapy.

And also to suppress thyroid-stimulating hormone in order to exclude the activation of tumor cells, which, as a rule, remain after surgery.

Consequences of the operation and their prevention

The most common complications after thyroid surgery are:

hoarseness, change in voice timbre up to its loss;
persistent paralysis of the muscles of the pharynx and larynx;
accidental removal of the parathyroid glands.

The first 2 groups of troubles are associated with damage to the recurrent laryngeal and accessory nerves. To prevent such consequences, pulse electromyography is used - the study of the passage of nerves by surgeons during surgery. The principle is quite simple: the device focuses on supplying impulses from motor nerves to muscles.

Forecast

The life expectancy of patients with thyroid cancer depends on a number of factors: the structure of the tumor, metastasis, the age and gender of the victim, and the presence of concomitant diseases. According to statistics, the survival rate for papillary cancer is about 90%, for follicular cancer - 80-85%. In other words, thyroid cancer is not always a death sentence; adequate treatment gives a chance for stable remission (no exacerbation of the disease).

Relapse is the repeated postoperative (after 6 months) appearance of the tumor.

This is interesting! The possibility of relapse is directly related to the structure of the tumor: according to statistics, with papillary cancer, relapse occurs in 16% of cases, follicular - 10%, poorly differentiated - 60-70%, anaplastic - 100%.

In general, the prognosis is favorable: less aggressive cancer - papillary - is more common. It responds well to treatment with optimistic results in the future.

An early detected tumor practically does not lead to a decrease in the patient’s life span. Follicular cancer is more difficult to cure due to rapid metastasis to distant organs. Undifferentiated forms of cancer tend to grow rapidly and metastasize early.

This is interesting! The average life expectancy after a verdict of “anaplastic cancer” is 1 year. The five-year survival rate for papillary cancer is 80% of cases, for follicular cancer it is 70%.

Relapse-free survival of patients is possible under the following circumstances:

small tumor size;
absence of metastases;
presence of a capsule;
successful performance of radical operations on the thyroid gland.

conclusions

Thyroid cancer is not uncommon, especially among young people on the planet. Outbreaks began to be recorded more frequently as a result of humanity's use of radioactive energy.

Nowadays there are many diagnostic methods for determining a malignant tumor - from primitive to the most sophisticated laboratory and instrumental ones, but none of them allows us to give a cancer verdict with 100% certainty. Clinical symptoms are not specific, and different types of neoplasms have their own morphological characteristics.

The most common type is relatively non-aggressive papillary cancer. Even taking into account the insidiousness of the disease, the prognosis is favorable: thyroid cancer is treated and, in general, the outcome is successful. But no one canceled preventive examinations.

After all, if you take care of your health, it will certainly reward you with the opportunity to enjoy life. And if unexpected turns happen, there is always a way out of the situation. We conclude the article with an optimistic phrase from the brilliant German writer Erich Maria Remarque: “As long as a person does not give up, he is stronger than his fate.”

We are ready to consider an equally important group of organic substances that have enormous biological significance. These substances are hormones. People familiar with biology associate the function of hormones in living organisms with the role of a virtuoso conductor in a large symphony orchestra. The conductor coordinates the work of orchestral groups, the entire large group of musicians, each of whom knows his part well and masterfully plays the instrument. However, it is obvious that without a conductor, the performance of a piece of music will very quickly turn into a meaningless alternation of sounds, and brilliant music into a terrible cacophony. Any living organism is a complex and unique system of organs and tissues, each of which performs its own integral and specific function. How is coordination and coordination of the work of all organs and systems of a living organism carried out? What plays the role of that very conductor’s baton that subordinates to a single goal and synchronizes the precious biological work of each organ and their systems? This most important function is performed by substances produced by the endocrine glands (or endocrine glands, as doctors call them); they are called hormones (from the Greek bogtao - to set in motion, to induce).

Hormones are biologically active organic substances that are produced by the endocrine glands and regulate the activity of organs and tissues of a living organism.

As you already know from the course of anatomy and physiology, hormones carry out humoral regulation of the activity of organs, organ systems and the entire organism as a whole. This is no less important type of regulation than the well-known nervous regulation.

It is clear that, while performing such numerous and varied functions, hormones also have a corresponding set of characteristic properties, among which the most important are:

Extremely high physiological activity - very small amounts of hormones cause very significant changes in the functioning of organs and tissues;

Remote action - the ability to regulate the functioning of organs remote from the gland that produces the hormone; this becomes possible because hormones, products of the endocrine glands, are delivered to these organs through the bloodstream;

Rapid destruction in tissues, since, having a very strong effect on the functioning of organs and tissues, hormones should not accumulate in them;

Continuous production (secretion) by the corresponding gland is caused by the need for constant regulation, a more or less strong impact on the work of the corresponding organ at each moment of time.

From the analysis of characteristic properties hormones, as a powerful means of humoral regulation, it is clear that their formation by the endocrine glands must at each moment of time exactly correspond to the state of the body. Ensuring this compliance is carried out according to the feedback principle: not only does the hormone influence the controlled organ system and the processes in it, but also the state of the system itself determines the productivity of the corresponding gland, the rate of formation and the amount of hormone produced. For example, a decrease in blood glucose concentration inhibits the secretion of insulin (a hormone that causes a decrease in glucose levels) and accelerates the secretion of glucagon (a hormone that stimulates an increase in blood glucose concentrations). Thus, thanks to the feedback principle, it is hormones that ensure homeostasis - the constancy of the composition of the internal environment of the body, control and regulation of the content of water, carbohydrates, electrolytes, etc. in it.

It is obvious that, influencing the work of numerous and various organs and tissues, regulating their production of chemical compounds of various compositions, hormones themselves must be diverse in structure and represent different classes of organic substances. According to their chemical structure, hormones are divided into:

Steroid (steroids);

Hormones are derivatives of amino acids;

Peptide;

Protein.

The classification of hormones is shown in Table 15.

Having become acquainted with the function of hormones in the body, let us dwell in more detail on their chemical structure. When considering the formulas of hormones, do not try to remember them, but simply get a general idea of the chemical nature of this group of biologically active substances.

Steroid hormones (steroids) can be formally considered as derivatives of the hypothetical hydrocarbon sterane.

Steroids can be divided into two groups: steroid sex hormones and adrenal hormones. Sex hormones, in turn, are divided into:

Estrogens are female sex hormones, or steroids, containing 18 carbon atoms in a molecule (the so-called C 18 compounds). These include, for example, estradiol C18H24O2.

The name of this hormone reflects the presence of two hydroxyl groups in the molecule. Obviously, the structure of the estradiol molecule allows it to be classified as both alcohols and phenols. Estrogens also include:

The presence of a carbonyl group is reflected in the name of estrone with the suffix -one; the name estriol clearly emphasizes the presence of three hydroxyl groups in its molecule;

Androgens are male sex hormones, or C 19 -steroids, the molecule of which is based on the skeleton of a hydrocarbon molecule with a complex structure - androstane:

The most important androgens are testosterone, dihydrotestosterone and androstanediol:

(the chemical name of testosterone is 17-hydroxy-4-androsten-3-one, dihydrotestosterone is 17-hydroxyandrostane-3-one).

It is obvious that testosterone is an unsaturated ketone alcohol, dihydrotestosterone and androstanediol can be considered as products of its hydrogenation, and the fact that androstanediol is a polyhydric alcohol and its saturated character is reflected in the name;

Progesterone and its derivatives, like estrogens, are female sex hormones and belong to C21 steroids.

From an analysis of the structure of the progesterone molecule, it is clear that it is a ketone and contains two carbonyl groups in the molecule. In addition to sex hormones, steroids also include adrenal hormones, such as cortisol, corticosterone and aldosterone.

Comparing the structural formulas of all these hormones, it is easy to notice that they have a lot in common, and of course, first of all, the “steroid core” of the molecule - four articulated carbo-cycles: three six-atomic and one pentaatomic.

Now, having an idea about steroids, let's get acquainted with hormones - derivatives of amino acids. These include the familiar thyroxine, adrenaline and norepinephrine.

The molecules of these hormones contain an amino group or its derivatives, and the thyroxine molecule also contains a carboxyl group, i.e. it is an a-amino acid and exhibits all the properties characteristic of amino acids.

Peptide hormones, for example vasopressin, have a more complex structure (symbols of amino acids are given in Table 7).

Vasopressin is a peptide hormone of the pituitary gland, having a relative molecular weight M r = 1084 and containing nine amino acid residues in the molecule. The pancreatic peptide hormone glucagon has an even larger relative molecular weight (about 3485). This is understandable, because its molecule contains 29 amino acid units. By denoting the amino acid residue with the symbol Am, the glucagon formula can be written as follows: H2N-(Am)29-COOH.

It is obvious that the glucagon molecule contains 28 peptide groups.

Note that the structures of glucagon in all vertebrates are similar or identical. This makes it possible to obtain glucagon medications from the pancreas of animals. And deciphering the structure of human glucagon made it possible to establish its synthesis in the laboratory.

Protein hormones contain in their molecules an even larger number of amino acid units, combined into one or more polypeptide chains. Thus, the insulin molecule contains 51 amino acid residues in two polypeptide chains, and the chains themselves are connected by two disulfide bridges. The relative molecular weight of human insulin is 5807. The establishment of the chemical structure of this protein made it possible to carry out its complete synthesis in the laboratory, to develop methods for transforming animal insulin into human insulin, and to produce this important hormone using genetic engineering methods.

Another protein hormone, somatotropin, has a relative molecular weight of about 21,500; the polypeptide chain of its molecule contains 191 amino acid residues and two disulfide bridges. At present, the primary structure of human, sheep, and bovine somatotropin has already been established.

It should be noted that the insulin molecules of large mammals differ in amino acid residues in only four positions out of 51, while the structure of somatotropin during the evolution of animals and humans underwent significant changes and this hormone acquired species specificity.

Now, knowing the composition and chemical structure of the most important hormones, let us consider their specific effect on various physiological processes. In this case, it would be logical to group hormones according to the endocrine glands that produce them.

Pancreatic hormones. Insulin is a polypeptide hormone already familiar to you (the first hormone that was synthesized chemically).

Insulin sharply increases the permeability of the walls of muscle and fat cells for glucose and does not affect the permeability of the walls of nerve cells - neurons. All processes of glucose absorption occur inside cells, and insulin promotes the transport of glucose in them, therefore, it ensures the absorption of glucose by the body, the synthesis of glycogen and its accumulation in muscle fibers.

With insufficient production of insulin in the body, one of the most severe endocrine diseases develops - diabetes mellitus, in which the liver and muscles sharply reduce the ability to absorb carbohydrates, primarily glucose.

A lack of carbohydrates (doctors say “sugars”) in cells causes acute cellular hunger, accompanied by an excess amount of glucose in the blood (hyperglycemia) and its excretion in the urine. Cells die from energy starvation, and the most valuable source of energy, glucose, is irretrievably lost by the body.

Diabetes mellitus can lead to failure of the limbs due to damage to the peripheral nerve nodes, visual impairment as a result of damage to the retinal vessels, impaired renal function, as well as the development of atherosclerosis - damage to the arteries and circulatory disorders.

The main treatment for diabetes mellitus is the use of insulin medications, strictly controlled by the attending physician.

By increasing the supply of glucose into adipose tissue cells, insulin promotes the formation of fat in the body.

This hormone increases the permeability of cell walls for amino acids, which means it stimulates protein synthesis in the cell.

Another hormone of the pancreas is glucagon, which stimulates the breakdown and hydrolysis of glycogen in cells to glucose and, thus, increases its content in the blood. In addition, it stimulates the breakdown of fats in adipose tissue cells. It is obvious that in its action glucagon is an insulin antagonist, i.e. a substance with the opposite effect on the body.

Thyroid hormones. The thyroid gland produces important hormones such as triiodothyronine, tetraiodothyronine (thyroxine) and thyrocalcitonin. The first two of them regulate energy metabolism in the body. Thus, when only 1 mg of thyroxine is introduced into the blood, a person’s daily energy consumption increases by more than 1000 kcal. Triiodothyronine is physiologically even more active, so its average content in the blood is 20-25 times less, and it is destroyed much faster in tissues. By stimulating a sharp increase in energy production, these hormones accelerate the consumption of all nutrients by cells - fats, carbohydrates, proteins, and increase tissue consumption of glucose from the blood, which, in turn, is compensated by an increase in the rate of glycogen hydrolysis in the liver. Triiodothyronine and thyroxine regulate not only energy processes in the body, but also plastic ones, that is, they accelerate the growth of the body. In addition, these hormones stimulate the central nervous system, speed up and make reflexes more pronounced, including tendon reflexes. It is therefore clear why hyperfunction of the thyroid

(glands - excessive production of hormones - leads to involuntary trembling (tremor) of the limbs, and a lack of iodine in food, necessary for the synthesis of triiodothyronine and thyroxine, causes the proliferation of thyroid tissue and the formation of goiter.

Adrenal hormones. The adrenal medulla produces adrenaline, which regulates many body functions, including the most important one - metabolism. The presence of this hormone accelerates the breakdown of glycogen in the liver and muscles, increasing the amount of glucose in the blood, which increases the performance of skeletal muscles when they are tired, and activates the excitability of visual and auditory receptors. Consequently, adrenaline is capable of stimulating a rapid increase in the body’s performance and resistance in emergency conditions.

The adrenal cortex produces several types of hormones: mineralocorticoids, such as aldosterone and corticosterone, which regulate mineral (salt) metabolism; glucocorticoids (cortisone, hydrocortisone), regulating protein, carbohydrate and fat metabolism; sex hormones (androgens, estrogens, progesterone), which regulate the development of the genital organs in childhood, when the secretion of the gonads is still insignificant (before puberty).

Of the mineralocorticoids, aldosterone is the most active. This hormone regulates the amount and balance of Na + and K + ions in the blood. Lack of aldosterone reduces the concentration of sodium chloride in the blood and tissue fluids, leading to a sharp decrease in blood pressure, dehydration and death of the body. Therefore, mineralocorticoids are often called life hormones. Obviously, their excess causes fluid retention in the body and a steady increase in blood pressure - hypertension (a more correct term from a medical point of view is arterial hypertension).

The most active of the glucocorticoids, the hormone hydrocortisone, stimulates the synthesis of glucose in the liver and thereby increases its content in the blood. The glycogen content in the liver does not decrease and may even increase. This is how the action of hydrocortisone differs fundamentally from the action of adrenaline. In addition, glucocorticoids accelerate the extraction of fats from adipose tissue and their oxidation (sometimes the metaphor “combustion” is used) to release the energy the body needs. The lack of these hormones depletes the body's strength, its resistance to adverse external influences and diseases. Therefore, doctors often call glucocorticoids anti-inflammatory hormones.

It is not surprising that under the influence of unfavorable factors that cause a state of nervous and physical tension, requiring the mobilization of protective forces (Canadian researcher Selye called this state “stress”), the body increases the secretion of glucocorticoids. As noted above, adrenaline “triggers” the acceleration of the synthesis of these hormones (now it is clear why it is sometimes called a dual-action hormone: it regulates some processes itself, and mobilizes mineralocorticoids to influence others). Thus, it is clear that the importance of adrenaline cannot be overestimated.

We are already a little familiar with gonadal hormones. Before reaching puberty, they are synthesized in the required quantities by the adrenal cortex. In adulthood, when the sexual function of the body becomes more important, the synthesis of androgens and estrogens begins to be carried out by special male and female sex glands of internal secretion.

Androgens, such as testosterone, regulate the formation and development of male secondary sexual characteristics - skeletal features, voice, distribution of body hair, behavior and, of course, the development and function of the male genital organs. Testosterone also stimulates nitrogen fixation in the body, thereby accelerating protein synthesis and muscle development. Therefore, testosterone, its preparations and related compounds - anabolic steroids (anabolics; from Greek - rise) - are used, for example, to accelerate muscle development in athletes.

When comparing the structure of the molecules of testosterone and estradiol - the main sex hormones familiar to you, you can note that they differ only slightly - by one methyl group and several hydrogen atoms. But how enormous are the consequences of these differences! Estradiol, like other estrogens, are female sex hormones, directs the development of the body according to the female type - is responsible for the formation of female secondary sexual characteristics, structural features of the body skeleton, behavior and character.

In addition to the pancreas, adrenal glands and gonads, hormones are also produced by another equally important gland - the pituitary gland.

1. Prepare by first consulting with; your biology teacher and school doctor, a short message about the basic means and methods of preventing diabetes.

Share the main ideas of your message with your family and friends.

2. What physiological processes correspond to the occurrence of adrenaline hyperglycemia? In what organs and tissues do these processes take place? Write an equation for the reaction of glycogen hydrolysis and explain the connection between this reaction and adrenaline hyperglycemia.

3. Describe the processes influenced by insulin and adrenaline. Can these hormones be considered antagonists?

4. What is called the endocrine system? Name the endocrine glands and the hormones they produce.

5. What processes does hydrocortisone regulate? What do the physiological actions of this hormone and adrenaline have in common? What distinguishes their effect on the body? Give reaction equations corresponding to the biochemical processes affected by these hormones.

6. What negative consequences can a continuous, prolonged elevated level of adrenaline in the blood lead to?

7. In diabetic coma - a severe complication of diabetes - a person loses consciousness, and life is threatened. Symptoms of an approaching coma are lethargy, drowsiness, loss of strength, and a sharp deterioration in well-being. Suggest first aid measures for a patient approaching coma. Check with your doctor or nurse to make sure your suggestions are correct.

8. What classes of substances include testosterone and estradiol? Why are the suffixes of their names different?

9. Anabolic steroids are synthetic drugs that stimulate protein synthesis and bone calcification. Their effect is manifested in an increase in skeletal mass and skeletal muscles. Compare the composition and structure of methandrostenolone - dianabol (formula I), phenobolin - durabolin (II, R=C(0)CH2CH2Ph), retabolil (II, R=CO(CH2)8(CH3) and trianabol (III):

All mammals, including humans, have hormones; they are also found in other living organisms. Plant hormones and insect molting hormones are well described.

The physiological action of hormones is aimed at: 1) providing humoral, i.e. carried out through the blood, regulation of biological processes; 2) maintaining the integrity and constancy of the internal environment, harmonious interaction between the cellular components of the body; 3) regulation of the processes of growth, maturation and reproduction.

In a normal state, there is a harmonious balance between the activity of the endocrine glands, the state of the nervous system and the response of target tissues (tissues that are targeted). Any violation in each of these links quickly leads to deviations from the norm. Excessive or insufficient production of hormones causes various diseases, accompanied by profound chemical changes in the body.

Endocrinology studies the role of hormones in the life of the body and the normal and pathological physiology of the endocrine glands. It appeared as a medical discipline only in the 20th century, but endocrinological observations have been known since antiquity. Hippocrates believed that human health and temperament depend on special humoral substances. Aristotle drew attention to the fact that a castrated calf, growing up, differs in sexual behavior from a castrated bull in that it does not even try to climb on a cow. In addition, castration has been practiced for centuries both to tame and domesticate animals and to transform humans into obedient slaves.

What are hormones? According to the classical definition, hormones are secretion products of endocrine glands that are released directly into the bloodstream and have high physiological activity. The main endocrine glands of mammals are the pituitary gland, thyroid and parathyroid glands, adrenal cortex, adrenal medulla, islet tissue of the pancreas, gonads (testes and ovaries), placenta and hormone-producing areas of the gastrointestinal tract. The body also synthesizes some compounds with hormone-like effects. For example, studies of the hypothalamus have shown that a number of substances it secretes are necessary for the release of pituitary hormones. These “releasing factors,” or liberins, have been isolated from various regions of the hypothalamus. They enter the pituitary gland through a system of blood vessels connecting both structures. Since the hypothalamus is not a gland in its structure, and releasing factors apparently enter only the very nearby pituitary gland, these substances secreted by the hypothalamus can be considered hormones only with a broad understanding of this term.

There are other problems in determining which substances should be considered hormones and which structures should be considered endocrine glands. It has been convincingly shown that organs such as the liver can extract physiologically inactive or completely inactive hormonal substances from the circulating blood and convert them into potent hormones. For example, dehydroepiandrosterone sulfate, a low-active substance produced by the adrenal glands, is converted in the liver into testosterone, a highly active male sex hormone secreted in large quantities by the testes. Does this prove, however, that the liver is an endocrine organ?

Other questions are even more difficult. The kidneys secrete the enzyme renin into the bloodstream, which, through activation of the angiotensin system (this system causes dilation of blood vessels), stimulates the production of the adrenal hormone aldosterone. The regulation of aldosterone release by this system is very similar to how the hypothalamus stimulates the release of the pituitary hormone ACTH (adrenocorticotropic hormone, or corticotropin), which regulates adrenal function. The kidneys also secrete erythropoietin, a hormonal substance that stimulates the production of red blood cells. Can the kidney be classified as an endocrine organ? All these examples prove that the classical definition of hormones and endocrine glands is not comprehensive enough.

Transport of hormones. Hormones, once in the bloodstream, must travel to the appropriate target organs. The transport of high molecular weight (protein) hormones has been little studied due to the lack of accurate data on the molecular weight and chemical structure of many of them. Hormones with a relatively small molecular weight, such as thyroid and steroid hormones, quickly bind to plasma proteins, so that the content of hormones in the blood in the bound form is higher than in the free form; these two forms are in dynamic equilibrium. It is the free hormones that exhibit biological activity, and in a number of cases it has been clearly shown that they are extracted from the blood by target organs.

The significance of protein binding of hormones in the blood is not entirely clear. It is believed that such binding facilitates the transport of the hormone or protects the hormone from loss of activity.

Action of hormones. The individual hormones and their main effects are presented below in the section "Major Human Hormones". In general, hormones act on specific target organs and cause significant physiological changes in them. A hormone can have multiple target organs, and the physiological changes it causes can affect a range of body functions. For example, maintaining normal blood glucose levels - which are largely controlled by hormones - is important for the functioning of the entire body. Hormones sometimes act together; Thus, the effect of one hormone may depend on the presence of some other hormone or other hormones. Growth hormone, for example, is ineffective in the absence of thyroid hormone.

The action of hormones at the cellular level is carried out by two main mechanisms: hormones that do not penetrate the cell (usually water-soluble) act through receptors on the cell membrane, and hormones that easily pass through the membrane (fat-soluble) act through receptors in the cytoplasm of the cell. In all cases, only the presence of a specific receptor protein determines the sensitivity of the cell to a given hormone, i.e. makes her a target. The first mechanism of action, studied in detail using the example of adrenaline, is that the hormone binds to its specific receptors on the cell surface; binding triggers a series of reactions that result in the formation of so-called. second messengers that have a direct effect on cellular metabolism. Such mediators are usually cyclic adenosine monophosphate (cAMP) and/or calcium ions; the latter are released from intracellular structures or enter the cell from the outside. Both cAMP and calcium ions are used to transmit external signals into cells in a wide variety of organisms at all levels of the evolutionary ladder. However, some membrane receptors, in particular insulin receptors, act in a shorter way: they penetrate the membrane right through, and when part of their molecule binds a hormone on the cell surface, the other part begins to function as an active enzyme on the side facing the inside of the cell; this ensures the manifestation of the hormonal effect.

The second mechanism of action - through cytoplasmic receptors - is characteristic of steroid hormones (adrenal and sex hormones), as well as thyroid hormones (T3 and T4). Having penetrated the cell containing the corresponding receptor, the hormone forms a hormone-receptor complex with it. This complex undergoes activation (with the help of ATP), after which it penetrates the cell nucleus, where the hormone has a direct effect on the expression of certain genes, stimulating the synthesis of specific RNA and proteins. It is these newly formed proteins, usually short-lived, that are responsible for the changes that constitute the physiological effect of the hormone.

The regulation of hormonal secretion is carried out by several interconnected mechanisms. They can be illustrated by the example of cortisol, the main glucocorticoid hormone of the adrenal glands. Its production is regulated by a feedback mechanism that operates at the level of the hypothalamus. When the level of cortisol in the blood decreases, the hypothalamus secretes corticoliberin, a factor that stimulates the pituitary gland to secrete corticotropin (ACTH). The increase in ACTH levels, in turn, stimulates the secretion of cortisol in the adrenal glands, and as a result, the level of cortisol in the blood increases. The increased level of cortisol then suppresses the release of corticoliberin via a feedback mechanism - and the content of cortisol in the blood decreases again.

Cortisol secretion is regulated not only by a feedback mechanism. For example, stress causes the release of corticoliberin, and, accordingly, the whole series of reactions that increase the secretion of cortisol. In addition, cortisol secretion follows a circadian rhythm; it is very high on awakening, but gradually decreases to a minimum level during sleep. Control mechanisms also include the rate of hormone metabolism and loss of activity. Similar regulatory systems operate in relation to other hormones.

Basic human hormones

Pituitary hormones are described in detail in the article PITUITARY Gland. Here we will only list the main products of pituitary secretion.

Hormones of the anterior pituitary gland. The glandular tissue of the anterior lobe produces:

– growth hormone (GH), or somatotropin, which affects all tissues of the body, increasing their anabolic activity (i.e., the processes of synthesis of body tissue components and increasing energy reserves).

– melanocyte-stimulating hormone (MSH), which enhances the production of pigment by some skin cells (melanocytes and melanophores);

– thyroid-stimulating hormone (TSH), which stimulates the synthesis of thyroid hormones in the thyroid gland;

– follicle-stimulating hormone (FSH) and luteinizing hormone (LH), related to gonadotropins: their action is aimed at the gonads.

– prolactin, sometimes referred to as PRL, is a hormone that stimulates the formation of mammary glands and lactation.

The hormones of the posterior lobe of the pituitary gland are vasopressin and oxytocin. Both hormones are produced in the hypothalamus but are stored and released in the posterior lobe of the pituitary gland, which lies inferior to the hypothalamus. Vasopressin maintains the tone of blood vessels and is an antidiuretic hormone that affects water metabolism. Oxytocin causes contractions of the uterus and has the property of “releasing” milk after childbirth.

Thyroid and parathyroid hormones. The thyroid gland is located in the neck and consists of two lobes connected by a narrow isthmus. The four parathyroid glands are usually located in pairs - on the posterior and lateral surfaces of each lobe of the thyroid gland, although sometimes one or two may be slightly displaced.

The main hormones secreted by the normal thyroid gland are thyroxine (T4) and triiodothyronine (T3). Once in the bloodstream, they bind - firmly but reversibly - to specific plasma proteins. T4 binds more strongly than T3 and is not released as quickly, so it acts more slowly but lasts longer. Thyroid hormones stimulate protein synthesis and nutrient breakdown, releasing heat and energy, which results in increased oxygen consumption. These hormones also influence carbohydrate metabolism and, along with other hormones, regulate the rate of mobilization of free fatty acids from adipose tissue. In short, thyroid hormones have a stimulating effect on metabolic processes. Increased production of thyroid hormones causes thyrotoxicosis, and when they are deficient, hypothyroidism or myxedema occurs.

Another compound found in the thyroid gland is long-acting thyroid stimulant. It is a gamma globulin and is likely to cause a hyperthyroid state.

The hormone produced by the parathyroid glands is called parathyroid hormone, or parathyroid hormone; it maintains a constant level of calcium in the blood: when it decreases, parathyroid hormone is released and activates the transfer of calcium from the bones into the blood until the calcium level in the blood returns to normal. Another hormone, calcitonin, has the opposite effect and is released when calcium levels in the blood are elevated. It was previously believed that calcitonin was secreted by the parathyroid glands, but now it has been shown that it is produced in the thyroid gland. Increased production of parathyroid hormone causes bone disease, kidney stones, calcification of the renal tubules, and a combination of these disorders is possible. Parathyroid hormone deficiency is accompanied by a significant decrease in the level of calcium in the blood and is manifested by increased neuromuscular excitability, spasms and convulsions.

Adrenal hormones. The adrenal glands are small structures located above each kidney. They consist of an outer layer called the cortex and an inner part called the medulla. Both parts have their own functions, and in some lower animals they are completely separate structures. Each of the two parts of the adrenal glands plays an important role both in normal health and in disease. For example, one of the hormones of the medulla - adrenaline - is necessary for survival, as it provides a reaction to sudden danger. When it occurs, adrenaline is released into the blood and mobilizes carbohydrate reserves for the rapid release of energy, increases muscle strength, causes dilation of the pupils and constriction of peripheral blood vessels. Thus, reserve forces are directed to “flight or fight”, and in addition, blood loss is reduced due to vasoconstriction and rapid blood clotting. Epinephrine also stimulates the secretion of ACTH (i.e., the hypothalamic-pituitary axis). ACTH, in turn, stimulates the adrenal cortex to release cortisol, resulting in an increase in the conversion of proteins into glucose, which is necessary to replenish glycogen stores in the liver and muscles used in the anxiety reaction.

The adrenal cortex secretes three main groups of hormones: mineralocorticoids, glucocorticoids and sex steroids (androgens and estrogens). Mineralocorticoids are aldosterone and deoxycorticosterone. Their action is associated primarily with maintaining salt balance. Glucocorticoids affect the metabolism of carbohydrates, proteins, fats, as well as immunological defense mechanisms. The most important of the glucocorticoids are cortisol and corticosterone. Sex steroids that play an auxiliary role are similar to those synthesized in the gonads; these are dehydroepiandrosterone sulfate, 4-androstenedione, dehydroepiandrosterone and some estrogens.

Excess cortisol leads to serious metabolic disturbances, causing hypergluconeogenesis, i.e. excessive conversion of proteins into carbohydrates. This condition, known as Cushing's syndrome, is characterized by loss of muscle mass, decreased carbohydrate tolerance, i.e. reduced supply of glucose from the blood to the tissues (which is manifested by an abnormal increase in the concentration of sugar in the blood when it comes from food), as well as demineralization of bones.

Excessive androgen secretion by adrenal tumors leads to masculinization. Adrenal tumors can also produce estrogens, especially in men, leading to feminization.

Hypofunction (reduced activity) of the adrenal glands occurs in acute or chronic form. Hypofunction is caused by a severe, rapidly developing bacterial infection: it can damage the adrenal gland and lead to deep shock. In the chronic form, the disease develops due to partial destruction of the adrenal gland (for example, by a growing tumor or tuberculosis) or the production of autoantibodies. This condition, known as Addison's disease, is characterized by severe weakness, weight loss, low blood pressure, gastrointestinal disturbances, increased salt requirements and skin pigmentation. Addison's disease, described in 1855 by T. Addison, became the first recognized endocrine disease.

Adrenaline and norepinephrine are the two main hormones secreted by the adrenal medulla. Epinephrine is considered a metabolic hormone due to its effects on carbohydrate storage and fat mobilization. Norepinephrine is a vasoconstrictor, i.e. it constricts blood vessels and increases blood pressure. The adrenal medulla is closely connected to the nervous system; Thus, norepinephrine is released by sympathetic nerves and acts as a neurohormone.

Excessive secretion of adrenal medulla hormones (medullary hormones) occurs with some tumors. Symptoms depend on which of the two hormones, adrenaline or norepinephrine, is produced in greater quantities, but the most common are sudden attacks of hot flashes, sweating, anxiety, palpitations, as well as headache and hypertension.

Testicular hormones. The testes (testes) have two parts, being glands of both external and internal secretion. As exocrine glands, they produce sperm, and the endocrine function is carried out by the Leydig cells they contain, which secrete male sex hormones (androgens), in particular 4-androstenedione and testosterone, the main male hormone. Leydig cells also produce small amounts of estrogen (estradiol).

The testes are under the control of gonadotropins (see section above PITUITARY HORMONES). The gonadotropin FSH stimulates sperm formation (spermatogenesis). Under the influence of another gonadotropin, LH, Leydig cells release testosterone. Spermatogenesis occurs only when there is a sufficient amount of androgens. Androgens, particularly testosterone, are responsible for the development of secondary sexual characteristics in men.

Violation of the endocrine function of the testes comes down in most cases to insufficient secretion of androgens. For example, hypogonadism is a decrease in testicular function, including testosterone secretion, spermatogenesis, or both. The cause of hypogonadism may be a disease of the testes, or, indirectly, a functional failure of the pituitary gland.

Increased androgen secretion occurs in Leydig cell tumors and leads to excessive development of male sexual characteristics, especially in adolescents. Sometimes testicular tumors produce estrogens, causing feminization. In the case of a rare tumor of the testes, choriocarcinoma, so many human chorionic gonadotropins are produced that testing a minimal amount of urine or serum gives the same results as in pregnant women. The development of choriocarcinoma can lead to feminization.

Ovarian hormones. The ovaries have two functions: developing eggs and secreting hormones. Ovarian hormones are estrogens, progesterone and 4-androstenedione. Estrogens determine the development of female secondary sexual characteristics. The ovarian estrogen, estradiol, is produced in the cells of the growing follicle, the sac that surrounds the developing egg. As a result of the action of both FSH and LH, the follicle matures and ruptures, releasing the egg. The ruptured follicle then turns into the so-called. corpus luteum, which secretes both estradiol and progesterone. These hormones, acting together, prepare the lining of the uterus (endometrium) for implantation of a fertilized egg. If fertilization does not occur, the corpus luteum undergoes regression; at the same time, the secretion of estradiol and progesterone stops, and the endometrium sloughs off, causing menstruation.

Although the ovaries contain many immature follicles, during each menstrual cycle only one of them matures and releases an egg. Excess follicles undergo reverse development throughout the reproductive period of a woman’s life. Degenerating follicles and remnants of the corpus luteum become part of the stroma, the supporting tissue of the ovary. Under certain circumstances, specific stromal cells are activated and secrete the precursor of active androgenic hormones - 4-androstenedione. Activation of the stroma occurs, for example, in polycystic ovary syndrome, a disease associated with impaired ovulation. As a result of this activation, excess androgens are produced, which can cause hirsutism (severe hairiness).

Reduced secretion of estradiol occurs with underdevelopment of the ovaries. Ovarian function also decreases during menopause, as the supply of follicles is depleted and, as a result, the secretion of estradiol decreases, which is accompanied by a number of symptoms, the most characteristic of which are hot flashes. Excess estrogen production is usually associated with ovarian tumors. The largest number of menstrual disorders are caused by an imbalance of ovarian hormones and ovulation disorders.

Hormones of the human placenta. The placenta is a porous membrane that connects the embryo (fetus) to the wall of the mother's uterus. It secretes human chorionic gonadotropin and human placental lactogen. Like the ovaries, the placenta produces progesterone and a number of estrogens.

Chorionic gonadotropin (CG). Implantation of a fertilized egg is facilitated by maternal hormones - estradiol and progesterone. On the seventh day after fertilization, the human embryo strengthens in the endometrium and receives nutrition from maternal tissues and from the bloodstream. Endometrial detachment, which causes menstruation, does not occur because the embryo secretes hCG, which preserves the corpus luteum: the estradiol and progesterone it produces maintains the integrity of the endometrium. After implantation of the embryo, the placenta begins to develop, continuing to secrete hCG, which reaches its highest concentration approximately in the second month of pregnancy. Determining the concentration of hCG in the blood and urine is the basis of pregnancy tests.

Human placental lactogen (PL). In 1962, PL was found in high concentrations in placental tissue, in blood flowing from the placenta, and in maternal peripheral blood serum. PL turned out to be similar, but not identical, to human growth hormone. It is a powerful metabolic hormone. By influencing carbohydrate and fat metabolism, it promotes the preservation of glucose and nitrogen-containing compounds in the mother’s body and thereby ensures that the fetus is supplied with a sufficient amount of nutrients; at the same time, it causes the mobilization of free fatty acids - the source of energy of the maternal body.

Progesterone. During pregnancy, the level of pregnanediol, a metabolite of progesterone, gradually increases in a woman's blood (and urine). Progesterone is secreted mainly by the placenta, and its main precursor is cholesterol from the mother's blood. Progesterone synthesis does not depend on precursors produced by the fetus, judging by the fact that it practically does not decrease several weeks after the death of the embryo; progesterone synthesis also continues in cases where the fetus was removed in patients with an abdominal ectopic pregnancy, but the placenta was preserved.

Estrogens. The first reports of high levels of estrogen in the urine of pregnant women appeared in 1927, and it soon became clear that such levels were maintained only in the presence of a living fetus. Later it was revealed that with fetal anomalies associated with impaired development of the adrenal glands, the content of estrogen in the mother’s urine is significantly reduced. This suggested that fetal adrenal hormones serve as precursors to estrogens. Further studies have shown that dehydroepiandrosterone sulfate, present in fetal plasma, is the main precursor of estrogens such as estrone and estradiol, and 16-hydroxydehydroepiandrosterone, also of fetal origin, is the main precursor of another placenta-produced estrogen, estriol. Thus, the normal excretion of estrogens in the urine during pregnancy is determined by two conditions: the fetal adrenal glands must synthesize precursors in the required quantity, and the placenta must convert them into estrogens.

Pancreatic hormones. The pancreas carries out both internal and external secretion. The exocrine (related to external secretion) component is the digestive enzymes, which in the form of inactive precursors enter the duodenum through the pancreatic duct. Internal secretion is provided by the islets of Langerhans, which are represented by several types of cells: alpha cells secrete the hormone glucagon, beta cells secrete insulin. The main effect of insulin is to lower blood glucose levels, carried out mainly in three ways: 1) inhibition of glucose formation in the liver; 2) inhibition in the liver and muscles of the breakdown of glycogen (a polymer of glucose, which the body can convert into glucose if necessary); 3) stimulation of glucose use by tissues. Insufficient secretion of insulin or its increased neutralization by autoantibodies leads to high blood glucose levels and the development of diabetes mellitus. The main effect of glucagon is to increase blood glucose levels by stimulating its production in the liver. Although insulin and glucagon primarily maintain physiological blood glucose levels, other hormones—growth hormone, cortisol, and adrenaline—also play a significant role.

Gastrointestinal hormones. Hormones of the gastrointestinal tract - gastrin, cholecystokinin, secretin and pancreozymin. These are polypeptides secreted by the mucous membrane of the gastrointestinal tract in response to specific stimulation. It is believed that gastrin stimulates the secretion of hydrochloric acid; cholecystokinin controls the emptying of the gallbladder, and secretin and pancreozymin regulate the secretion of pancreatic juice.

Neurohormones are a group of chemical compounds secreted by nerve cells (neurons). These compounds have hormone-like properties, stimulating or inhibiting the activity of other cells; these include the previously mentioned releasing factors, as well as neurotransmitters, whose function is to transmit nerve impulses through the narrow synaptic cleft that separates one nerve cell from another. Neurotransmitters include dopamine, epinephrine, norepinephrine, serotonin, histamine, acetylcholine and gamma-aminobutyric acid.

In the mid-1970s, a number of new neurotransmitters were discovered that have morphine-like analgesic effects; they are called “endorphins”, i.e. "internal morphines". Endorphins are able to bind to special receptors in brain structures; As a result of this binding, impulses are sent to the spinal cord that block the conduction of incoming pain signals. The analgesic effect of morphine and other opiates is undoubtedly due to their similarity to endorphins, ensuring their binding to the same pain-blocking receptors.

Therapeutic uses of hormones

Hormones were initially used in cases of insufficiency of any of the endocrine glands to replace or replenish the resulting hormonal deficiency. The first effective hormonal drug was an extract of the sheep thyroid gland, used in 1891 by the English doctor G. Murray to treat myxedema. Today, hormonal therapy can compensate for the insufficient secretion of almost any endocrine gland; Replacement therapy carried out after removal of a particular gland also produces excellent results. Hormones can also be used to stimulate the glands. Gonadotropins, for example, are used to stimulate the gonads, in particular to induce ovulation.

In addition to replacement therapy, hormones and hormone-like drugs are used for other purposes. Thus, excessive secretion of androgen by the adrenal glands in some diseases is suppressed with cortisone-like drugs. Another example is the use of estrogens and progesterone in birth control pills to suppress ovulation.

Hormones can also be used as agents that neutralize the effects of other medications; in this case, they proceed from the fact that, for example, glucocorticoids stimulate catabolic processes, and androgens stimulate anabolic processes. Therefore, against the background of a long course of glucocorticoid therapy (say, in the case of rheumatoid arthritis), anabolic agents are often additionally prescribed to reduce or neutralize its catabolic effect.

Hormones are often used as specific medications. Thus, adrenaline, which relaxes smooth muscles, is very effective in cases of an attack of bronchial asthma. Hormones are also used for diagnostic purposes. For example, when studying the function of the adrenal cortex, they resort to its stimulation by injecting the patient with ACTH, and the response is assessed by the content of corticosteroids in the urine or plasma.

Currently, hormone preparations have begun to be used in almost all areas of medicine. Gastroenterologists use cortisone-like hormones in the treatment of regional enteritis or mucous colitis. Dermatologists treat acne with estrogens, and some skin diseases with glucocorticoids; Allergists use ACTH and glucocorticoids in the treatment of asthma, urticaria and other allergic diseases. Pediatricians use anabolic agents when it is necessary to improve appetite or speed up a child's growth, as well as large doses of estrogen to close the epiphyses (growing parts of bones) and thus prevent excessive growth.

During organ transplantation, glucocorticoids are used, which reduce the chances of transplant rejection. Estrogens can limit the spread of metastatic breast cancer in postmenopausal patients, and androgens are used for the same purpose before menopause. Urologists use estrogens to slow the spread of prostate cancer. Internal medicine specialists have found it useful to use cortisone-like compounds in the treatment of certain types of collagen diseases, and gynecologists and obstetricians use hormones in the treatment of many disorders not directly related to hormonal deficiency.

Invertebrate hormones

Invertebrate hormones have been studied mainly in insects, crustaceans and mollusks, and much in this area still remains unclear. Sometimes the lack of information about the hormones of a particular animal species is simply explained by the fact that this species does not have specialized endocrine glands, and individual groups of cells that secrete hormones are difficult to detect.

It is likely that any function regulated by hormones in vertebrates is similarly regulated in invertebrates. In mammals, for example, the neurotransmitter norepinephrine increases the heart rate, and in the crab Cancer pagurus and the lobster Homarus vulgaris, the same role is played by neurohormones - biologically active substances produced by neurosecretory cells of the nervous tissue. Calcium metabolism in the body is regulated in vertebrates by the hormone of the parathyroid glands, and in some invertebrates - by a hormone produced by a special organ located in the thoracic region of the body. Many other functions in invertebrates are also subject to hormonal regulation, including metamorphosis, movement and rearrangement of pigment granules in chromatophores, respiration rate, maturation of germ cells in the gonads, formation of secondary sexual characteristics and body growth.

Metamorphosis. Observations on insects have revealed the role of hormones in the regulation of metamorphosis, and several hormones have been shown to do so. We will focus on the two most important hormone antagonists. At each of those stages of development that are accompanied by metamorphosis, neurosecretory cells of the insect brain produce the so-called. a brain hormone that stimulates the synthesis of the steroid hormone that induces molting, ecdysone, in the prothoracic (prothoracic) gland. At the same time that ecdysone is synthesized in the insect’s body, the so-called corpora allata is produced in the adjacent bodies (corpora allata) - two small glands located in the insect’s head. juvenile hormone, which suppresses the action of ecdysone and ensures the next larval stage after molting. As the larva grows, less and less juvenile hormone is produced and, finally, its amount is no longer sufficient to prevent molting. For example, in butterflies, a decrease in the level of juvenile hormone leads to the fact that the last larval stage after molting turns into a pupa.

The interaction of hormones regulating metamorphosis has been demonstrated in a number of experiments. For example, it is known that the bug Rhodnius prolixus undergoes five molts during its normal life cycle before becoming an adult form (imago). If, however, the larvae are decapitated, then the surviving metamorphoses will be shortened and they will develop, although miniature, but otherwise normal adult forms. The same phenomenon can be observed in the larva of the cecropian silkworm butterfly (Samia cecropia), if the adjacent bodies are removed and thereby eliminate the synthesis of juvenile hormone. In this case, just like in Rhodnius, the metamorphosis will be shortened and the adult forms will be smaller than usual. And vice versa, if the adjacent bodies of a young cecropium silkworm caterpillar are transplanted into a larva that is already ready to turn into an adult, then the metamorphosis will be delayed and the larvae will be larger than usual.

Juvenile hormone has recently been synthesized and can now be obtained in large quantities. Experiments have shown that if the hormone is exposed in high concentrations to insect eggs or at another stage of their development, when this hormone is normally absent, then serious metabolic disorders occur, leading to the death of the insect. This result allows us to hope that the synthetic hormone will turn out to be a new and very effective means of combating insect pests. Compared to chemical insecticides, juvenile hormone has a number of important advantages. It does not affect the life activity of other organisms, unlike pesticides that seriously disrupt the ecology of entire regions. Equally important, an insect may eventually develop resistance to any pesticide, but it is unlikely that any insect will develop resistance to its own hormones.

Reproduction. Experiments suggest that hormones are involved in insect reproduction. In mosquitoes, for example, they regulate both egg formation and laying. When a female mosquito digests the portion of blood she has absorbed, the walls of the stomach and abdomen stretch, which serves as a trigger for the transmission of impulses to the brain. After about an hour, special cells in the upper part of the brain release a hormone into the hemolymph (“blood”) circulating in the body cavity, which stimulates the secretion of another hormone from two glands located in the constriction area, or cervix. This second hormone stimulates not only the maturation of eggs, but also the storage of nutrients in them. In mature female mosquitoes, during daylight hours, under the influence of light, a special hormone is released into the corresponding centers of the nervous system that stimulates the laying of eggs, which usually occurs in the afternoon, i.e. still in the daytime. With an artificial change from night to day, this order can be disrupted: in experiments with the mosquito Aedes aegypti (the carrier of yellow fever), females laid eggs at night if they were kept in lighted cages at night and in darkened cages during the day. In most species of insects, egg laying is stimulated by a hormone produced by a certain part of the adjacent bodies.

In cockroaches, grasshoppers, bedbugs and flies, ovarian maturation depends on one of the hormones secreted by the adjacent bodies; in the absence of this hormone, the ovaries do not mature. In turn, the ovaries produce hormones that affect the adjacent bodies. Thus, when the ovaries were removed, degeneration of the adjacent bodies was observed. If mature ovaries were transplanted into such an insect, then after some time the normal size of the adjacent bodies was restored.

Sex differences. Many invertebrates, including insects, are characterized by sexual dimorphism, i.e. difference in morphological characteristics in males and females. In mosquitoes, for example, the female feeds on the blood of mammals and her mouthparts are adapted to pierce the skin, while the males feed on nectar or plant juices and have a longer and thinner proboscis. In bees, sexual dimorphism clearly correlates with the characteristics of the behavior and fate of each caste of individuals: males (drones) serve only for reproduction and die after the mating flight, females are represented by two castes - the queen (queen), which has a developed reproductive system and participates in reproduction, and sterile worker bees. Observations and experiments carried out on bees and other invertebrates show that the development of sexual characteristics is regulated by hormones that are produced by the gonads.

In many crustaceans, the male sex hormone (androgen) is produced by the androgen gland located in the vas deferens. This hormone is necessary for the formation of testes and accessory (copulatory) genital organs, as well as for the development of secondary sexual characteristics. When the androgen gland is removed, both body shape and function change, so that the castrated male ends up looking like a female.

Change in color. The ability to change body color is characteristic of many invertebrates, including insects, crustaceans and mollusks. The Dixippus stick insect appears green on a green background, but on a darker background it resembles a stick, as if covered with bark. In stick insects, like many other organisms, changing body color depending on the color of the background is one of the main means of defense, allowing the animal to evade the attention of a predator.

In the body of invertebrates capable of changing body color, hormones are produced that stimulate the movement and rearrangement of pigment granules. Both in the light and in the dark, the green pigment is distributed evenly in the chromatophores, so in the daytime the stick insect is colored green. Under illuminated background conditions, granules of brown and red pigments are grouped along the edges of the cell. When darkness sets in or light decreases, granules of dark pigments disperse and the insect takes on the color of tree bark. The chromatophore response is caused by a neurohormone released by the brain in response to changes in background illumination. Under the influence of light, this hormone enters the blood and is delivered to the target cell. Other insect hormones that regulate the movement of pigments enter the blood from the adjacent bodies and from the ganglion (nerve ganglion) located under the esophagus.

Retinal pigments in the compound eye of crustaceans also move in response to changes in light, and this adaptation to light is subject to hormonal regulation. Squid and other shellfish also have pigment cells whose response to light is regulated by hormones. Squid chromatophores contain blue, purple, red and yellow pigments. With appropriate stimulation, his body can take on different colors, which gives him the ability to instantly adapt to his environment.

The mechanisms that control the movement of pigments in chromatophores are different. The Eledone octopus has fibers in its chromatophores that can contract in response to the action of tyramine, a hormone produced by the salivary gland. When they contract, the area occupied by the pigments expands and the octopus’s body darkens. When the fibers relax in response to another hormone, betaine, the area contracts and the body brightens.

A different mechanism for the movement of pigments has been found in the skin cells of insects, in the retinal cells of some crustaceans and in cold-blooded vertebrates. In these animals, pigment granules are associated with high-polymer protein molecules that are capable of transitioning from a sol to a gel state and back. Upon transition to the gel state, the volume occupied by protein molecules decreases and pigment granules collect in the center of the cell, which is observed in the dark phase. In the light phase, protein molecules pass into the sol state; this is accompanied by an increase in their volume and dispersion of granules throughout the cell.

Vertebrate hormones

All vertebrates have the same or very similar hormones, and in mammals the similarity is so great that some hormonal preparations obtained from animals are used for injection in humans. Sometimes, however, a particular hormone acts differently in different species. For example, estrogen produced by the ovaries affects feather growth in Leghorn chickens but does not affect feather growth in pigeons.

Not all studies on the role of hormones allow us to draw clear conclusions. For example, data regarding the role of hormones in bird migrations is contradictory. In some species, notably the winter junco, the gonads become larger in spring as day length increases, suggesting that hormones initiate migration. However, this reaction is not observed in other bird species. The role of hormones in such a phenomenon as hibernation in mammals is also unclear.

Thyroxine, a vertebrate thyroid hormone produced by the thyroid gland, regulates basal metabolism and developmental processes. Experiments have shown that in reptiles, for example, periodic molting is, at least in part, regulated by thyroxine.

In amphibians, the function of thyroxine has been best studied in frogs. Tadpoles fed thyroid extract stopped growing and early turned into small adult frogs, i.e. they experienced accelerated metamorphosis. When their thyroid gland was removed, metamorphosis did not occur and they remained tadpoles.

Thyroxine also plays an important role in the life cycle of another amphibian, the tiger ambystoma. The neotenic (capable of reproduction) Ambystoma larva - axolotl - usually does not undergo metamorphosis, remaining at the larval stage. However, if you add a small amount of bovine thyroid extract to the axolotl's food, metamorphosis will occur and the axolotl will develop into a small black air-breathing ambystoma.

Water and ion balance. In amphibians and mammals, diuresis (urination) is stimulated by hydrocortisone, a hormone secreted by the adrenal cortex. The opposite - depressing - effect on diuresis is exerted by another hormone, which is produced by the hypothalamus, enters the posterior lobe of the pituitary gland, and from it into the systemic circulation.

All vertebrates, with the exception of fish, have parathyroid glands that secrete a hormone that helps maintain the balance of calcium and phosphorus. Apparently, in bony fish the function of the parathyroid glands is performed by some other structures, but this has not yet been established for sure. Other hormones involved in metabolism, regulating the balance of potassium, sodium and chlorine ions, are secreted by the adrenal cortex and the posterior lobe of the pituitary gland. Hormones of the adrenal cortex increase the content of sodium and chlorine ions in the blood of mammals, reptiles and frogs.

Insulin. The two hormones that regulate blood sugar, insulin and glucagon, are produced by specialized cells of the pancreas that make up the islets of Langerhans. There are four types of cells: alpha, beta, C and D. The proportion of these cell types varies in different groups of animals, and a number of amphibians have only beta cells. Some fish species do not have a pancreas and the islet tissue is found in their intestinal wall; there are also species in which it is located in the liver. There are known fish in which accumulations of islet tissue are presented in the form of separate endocrine glands. The hormones secreted by islet cells—insulin and glucagon—apparently perform the same function in all vertebrates.

Pituitary hormones. The pituitary gland secretes a variety of hormones; their action is well known from observations on mammals, but they play the same role in all other groups of vertebrates. If, for example, a hibernating female frog is injected with an extract from the anterior pituitary gland, this will stimulate the maturation of eggs and she will begin to lay eggs. In the African weaver, the gonadotropic hormone produced by the anterior pituitary gland initiates the secretion of the male sex hormone by the testes. This hormone stimulates the expansion of the efferent tubules of the testis, as well as the formation of melanin pigment in the beak and, as a result, the darkening of the beak. In the same African weaver, the luteinizing hormone produced by the posterior lobe of the pituitary gland initiates the synthesis of pigments in some feathers and the secretion of progesterone by the corpus luteum of the ovary.

Body color changes in cold-blooded animals, such as chameleons and some fish, are regulated by another pituitary hormone, namely melanocyte-stimulating hormone (MSH), or intermedin. This hormone is also present in birds and mammals, but in most cases it does not have any effect on pigmentation. The presence of MSH in the body of birds and mammals, where this hormone apparently does not play a noticeable role, allows us to make a number of assumptions about the evolution of vertebrates.

Bibliography

Dogel V.A. Zoology of invertebrates. M., 1981

Tepperman J., Tepperman H. Physiology of metabolism and the endocrine system. M., 1989

Hadorn E., Wehner. R. General zoology. M., 1989

Alberts B., Bray D., Lewis J., Raff M., Roberts K., Watson J. Molecular biology of cells, vol. 2. M., 1994

Human Physiology, ed. Schmidt R., Tevsa G., vols. 2–3. M., 1996

1. What substances are called hormones? What are their main properties?

Hormones are chemical compounds with high biological activity, secreted by the endocrine glands.

Properties of hormones:

produced in small quantities;
distant nature of action (the organs and systems on which hormones act are located far from the place of their formation, so hormones are distributed throughout the body through the bloodstream);
remain active for a long time;
strict specificity of action;
high biological activity;
regulate metabolic processes, ensure the constancy of the composition of the environment, influence the growth and development of organs, and ensure the body’s response to the influence of the external environment.

According to their chemical nature, hormones are divided into three groups: polypeptides and proteins (insulin); amino acids and their derivatives (thyroxine, adrenaline); steroids (sex hormones).

If an increased amount of hormones is formed and released into the blood, this is hyperfunction. If the amount of hormones produced and released into the blood decreases, then this is hypofunction.

2. Which glands produce hormones? Name them. What effect do the hormones of these glands have on the body?

The thyroid gland is located in the neck, in front of the larynx, and produces hormones rich in iodine - thyroxine, etc. They stimulate metabolism in the body. The level of oxygen consumption by organs and tissues of the body depends on their quantity in the blood, i.e. Thyroid hormones stimulate oxidative processes in cells. In addition, they regulate water, protein, fat, carbohydrate, mineral metabolism, growth and development of the body. They have an effect on the functions of the central nervous system and higher nervous activity. Lack of the hormone in childhood leads to cretinism (growth, sexual and mental development are delayed, body proportions are disturbed). With hypofunction, an adult develops myxedema (decreased metabolism, obesity, decreased body temperature, apathy). With hyperfunction in adults, Graves' disease occurs (enlargement of the thyroid gland, development of goiter, bulging eyes, increased metabolism, increased excitability of the nervous system).

Adrenal glands. Small bodies above the kidneys. They consist of two layers: outer (cortical) and inner (cerebral). The external substance produces hormones that regulate metabolism (sodium, potassium, proteins, carbohydrates, fats), and sex hormones (determine the development of secondary sexual characteristics). With insufficient function of the adrenal cortex, a disease develops, which is called bronze disease. The skin acquires a bronze color, increased fatigue, loss of appetite, and nausea are observed. With hyperfunction of the adrenal glands, there is an increase in the synthesis of sex hormones. At the same time, secondary sexual characteristics change. For example, women develop a mustache, beard, etc.

The internal substance produces the hormones adrenaline and norepinephrine. Adrenaline accelerates blood circulation, increases heart rate, mobilizes all the body's forces in stressful situations, and increases blood sugar (breaks down glycogen). The amount of adrenaline is under the control of the central nervous system; there is no shortage. When in excess, it increases the heart rate and constricts blood vessels. Norepinephrine slows down the heart rate.

Pancreas. Located in the abdominal cavity of the body, below the stomach. This is a mixed secretion gland, has excretory ducts and secretes enzymes involved in digestion. Individual cells of the pancreas release hormones into the blood. One group of cells produces the hormone glucagon, which helps convert liver glycogen into glucose, causing blood sugar levels to rise. Other cells produce insulin. This is the only hormone that lowers blood sugar (promotes the synthesis of glycogen in liver cells). When pancreatic function is insufficient, diabetes mellitus develops. At the same time, the blood sugar level increases. Carbohydrates are not retained in the body, but are excreted in the urine in the form of glucose.

The sex glands - testes in men and ovaries in women - also belong to the glands of mixed secretion. Due to the exocrine function, sperm and eggs are formed. Endocrine function is associated with the production of male and female sex hormones, which regulate the development of secondary sexual characteristics. They influence body formation, metabolism and sexual behavior. Androgens are produced in the testes. They stimulate the development of secondary sexual characteristics characteristic of men (growth of a beard, mustache, muscle development, etc.), increase basal metabolism, and are necessary for the maturation of sperm.

The ovaries produce female sex hormones - estrogens, under the influence of which the formation of secondary sexual characteristics characteristic of women occurs (body shape, development of the mammary glands, etc.) Material from the site

Pituitary. It is located below the pons of the brain and consists of three lobes: anterior, intermediate and posterior. The anterior lobe secretes growth hormone, which affects the growth of bones in length, accelerates metabolic processes, leads to increased growth, and an increase in body weight. Hormone deficiency results in dwarfism, but body proportions and mental development are not impaired. Hyperfunction in childhood leads to gigantism (children have long limbs and are not physically strong enough); in adults, acromegaly occurs (the size of the hand, foot, facial part of the skull, nose, lips, chin increases). Hypofunction in adults leads to changes in metabolism: either obesity or sudden weight loss.

The intermediate lobe of the pituitary gland secretes a hormone that affects skin pigmentation.

The posterior lobe is formed by nervous tissue. It does not synthesize hormones. Biologically active substances produced by the nuclei of the hypothalamus are transported to the posterior lobe of the pituitary gland. One of them selectively affects the contractions of the smooth muscles of the uterus and the secretion of the mammary glands. Another increases blood pressure and delays urine output. When the amount of this substance decreases, urination increases to 10-20 liters. per day. This disease is called diabetes insipidus.

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Completed by a 9b grade student

Baranova Yulia

ENDOCRINE SYSTEM - a system of glands that produce hormones and release them directly into the blood.

Introduction

These glands, called endocrine or endocrine glands, do not have excretory ducts; they are located in different parts of the body, but are functionally closely interconnected

THE CONCEPT OF HORMONES

Hormones are organic compounds produced by certain cells and designed to control, regulate and coordinate body functions. Higher animals have two regulatory systems with the help of which the body adapts to constant internal and external changes. One of them is the nervous system, which quickly transmits signals (in the form of impulses) through a network of nerves and nerve cells; the other is endocrine, which carries out chemical regulation with the help of hormones that are carried in the blood and have an effect on tissues and organs remote from the place of their release. The chemical communication system interacts with the nervous system; Thus, some hormones function as mediators (messengers) between the nervous system and the organs that respond to the influence. Thus, the distinction between neural and chemical coordination is not absolute.
Hormones discovered in 1902 by Starling and Bayliss
All mammals, including humans, have hormones; they are also found in other living organisms. Plant hormones and insect molting hormones are well described.
The physiological action of hormones is aimed at: 1) providing humoral, i.e. carried out through the blood, regulation of biological processes; 2) maintaining the integrity and constancy of the internal environment, harmonious interaction between the cellular components of the body; 3) regulation of the processes of growth, maturation and reproduction.

Hormones regulate the activity of all cells in the body. They affect mental acuity and physical mobility, physique and height, determine hair growth, tone of voice, sex drive and behavior. Thanks to the endocrine system, a person can adapt to strong temperature fluctuations, excess or lack of food, and physical and emotional stress. The study of the physiological action of the endocrine glands made it possible to reveal the secrets of sexual function and the miracle of childbirth, as well as answer the question of why some people are tall and others are short, some are fat, others are thin, some are slow, others are agile, some are strong, others are weak.
In a normal state, there is a harmonious balance between the activity of the endocrine glands, the state of the nervous system and the response of target tissues (tissues that are targeted). Any violation in each of these links quickly leads to deviations from the norm. Excessive or insufficient production of hormones causes various diseases, accompanied by profound chemical changes in the body.
Endocrinology studies the role of hormones in the life of the body and the normal and pathological physiology of the endocrine glands. It appeared as a medical discipline only in the 20th century, but endocrinological observations have been known since antiquity. Hippocrates believed that human health and temperament depend on special humoral substances. Aristotle drew attention to the fact that a castrated calf, growing up, differs in sexual behavior from a castrated bull in that it does not even try to climb on a cow. In addition, castration has been practiced for centuries both to tame and domesticate animals and to transform humans into obedient slaves.
What are hormones? According to the classical definition, hormones are secretion products of endocrine glands that are released directly into the bloodstream and have high physiological activity. The main endocrine glands of mammals are the pituitary gland, thyroid and parathyroid glands, adrenal cortex, adrenal medulla, islet tissue of the pancreas, gonads (testes and ovaries), placenta and hormone-producing areas of the gastrointestinal tract. The body also synthesizes some compounds with hormone-like effects. For example, studies of the hypothalamus have shown that a number of substances it secretes are necessary for the release of pituitary hormones. These “releasing factors,” or liberins, have been isolated from various regions of the hypothalamus. They enter the pituitary gland through a system of blood vessels connecting both structures. Since the hypothalamus is not a gland in its structure, and releasing factors apparently enter only the very nearby pituitary gland, these substances secreted by the hypothalamus can be considered hormones only with a broad understanding of this term.
There are other problems in determining which substances should be considered hormones and which structures should be considered endocrine glands. It has been convincingly shown that organs such as the liver can extract physiologically inactive or completely inactive hormonal substances from the circulating blood and convert them into potent hormones. For example, dehydroepiandrosterone sulfate, a low-active substance produced by the adrenal glands, is converted in the liver into testosterone, a highly active male sex hormone secreted in large quantities by the testes. Does this prove, however, that the liver is an endocrine organ?
Other questions are even more difficult. The kidneys secrete the enzyme renin into the bloodstream, which, through activation of the angiotensin system (this system causes dilation of blood vessels), stimulates the production of the adrenal hormone aldosterone. The regulation of aldosterone release by this system is very similar to how the hypothalamus stimulates the release of the pituitary hormone ACTH (adrenocorticotropic hormone, or corticotropin), which regulates adrenal function. The kidneys also secrete erythropoietin, a hormonal substance that stimulates the production of red blood cells. Can the kidney be classified as an endocrine organ? All these examples prove that the classical definition of hormones and endocrine glands is not comprehensive enough.

CLASSIFICATION OF HORMONES. MECHANISM OF ACTION OF HORMONES.
The hormones themselves do not directly affect any cell reactions. Only by contacting a certain receptor, unique to it, a certain reaction is caused.
Hormones have different chemical structures. This leads to the fact that they have different physical properties. Hormones are divided into water- and fat-soluble. Belonging to one of these classes determines their mechanism of action. This is explained by the fact that fat-soluble hormones can easily penetrate the cell membrane, which consists primarily of a lipid bilayer, while water-soluble hormones cannot do this. In this regard, receptors (R) for water- and fat-soluble hormones have different locations (membrane and cytoplasm). Having bound to the membrane receptor, the hormone causes a cascade of reactions in the cell itself, but does not in any way affect the genetic material. The complex of cytoplasmic P and hormone can affect nuclear receptors and cause changes in the genetic apparatus, which leads to the synthesis of new proteins. Let's look at this in more detail.

MECHANISM OF ACTION OF STEROID (FAT SOLUBLE) HORMONES.
I. Penetration of steroid (C) into the cell
II. Formation of the SR complex
All P steroid hormones are globular proteins of approximately the same size, binding hormones with a very high affinity
III. Transformation of CP into a form capable of binding by nuclear acceptors [CP]
Any cell contains all genetic information. However, with cell specialization, most of the DNA loses the ability to serve as a template for mRNA synthesis. This is achieved by folding histone proteins around proteins, which leads to an obstacle to transcription. In this regard, the genetic material of a cell can be divided into 3 types of DNA:
1.transcriptionally inactive
2. constantly expressed
3. induced by hormones or other signaling molecules.
IV. Binding of [CP] to a chromatin acceptor
It should be noted that this stage of action has not been fully studied and has a number of controversial issues. It is believed that [CP] interacts with specific regions of DNA in such a way that this allows RNA polymerase to come into contact with certain DNA domains.

An interesting experience is that it has shown that the half-life of mRNA increases when stimulated by a hormone. This leads to an increase in the amount of mRNA? Many contradictions: it becomes unclear whether there is evidence that [CP] increases the transcription rate or increases the half-life of mRNA; at the same time, the increase in the half-life of mRNA is explained by the presence of a large number of ribosomes in a hormone-stimulated cell, which stabilize mRNA or by another action [SR] unknown to us at the moment.
V. Selective initiation of transcription of specific mRNAs; coordinated synthesis of tRNA and rRNA

It can be assumed that the main effect of [CP] is the loosening of condensed chromatin, which leads to opening access to RNA polymerase molecules. An increase in the amount of mRNA leads to an increase in the synthesis of tRNA and rRNA.
VI. Processing of primary RNAs
VII. Transport of mRNA into the cytoplasm
VIII. Protein synthesis
IX. Post-translational modification of protein.
However, as research shows, this is the main, but not the only possible mechanism of action of hormones. For example, androgens and estrogens cause an increase in cAMP in some cells, which suggests that there are also membrane receptors for steroid hormones. This shows that steroid hormones act on some sensitive cells like water-soluble hormones.

SECONDARY INTERMEDIARIES
Peptide hydrophilic compounds - hormones, amines and neurotransmitters, unlike steroids, are not able to easily penetrate the plasma membrane of the cell. Therefore, they interact with membrane receptors located on the cell surface. Hormone-receptor interaction initiates a highly coordinated biological reaction, in which many cellular components may participate, some of them located at a significant distance smell from the plasma membrane. the first compound that Sutherland, who discovered it, called cAMP the “second messenger,” because he considered the “first messenger” to be the hormone itself, which causes intracellular synthesis of the “second messenger,” which mediates biological Chinese effect of the first.
Today, we can name at least 3 types of second messengers: 1) cyclic nucleotides (cAMP and cGMP); 2) Ca ions and 3) phosphatidylinositol metabolites.
With the help of such systems, a small number of hormone molecules, binding to receptors, causes the production of a much larger number of second messenger molecules, and the latter, in turn, influence the activity of an even larger number protein molecules. Thus, there is a progressive amplification of the signal that initially appears when the hormone binds to the cAMP receptor
In a simplified way, the action of the hormone through cAMP can be represented as follows:
1. hormone + stereospecific receptor
2. activation of adenylate cyclase
3. cAMP formation
4. ensuring cAMP coordinated reaction

CONCLUSION
Hormones were initially used in cases of insufficiency of any of the endocrine glands to replace or replenish the resulting hormonal deficiency. The first effective hormonal drug was an extract of the sheep thyroid gland, used in 1891 by the English physician G. Murray to treat myxedema. Today, hormonal therapy can compensate for the insufficient secretion of almost any endocrine gland; Replacement therapy carried out after removal of a particular gland also produces excellent results. Hormones can also be used to stimulate the glands.
Currently, hormone preparations have begun to be used in almost all areas of medicine. Gastroenterologists use cortisone-like hormones in the treatment of regional enteritis or mucous colitis. Dermatologists treat acne with estrogens, and some skin diseases with glucocorticoids; Allergists use ACTH and glucocorticoids in the treatment of asthma, urticaria and other allergic diseases. Pediatricians use anabolic agents when it is necessary to improve appetite or speed up a child's growth, as well as large doses of estrogen to close the epiphyses (growing parts of bones) and thus prevent excessive growth.
etc.................