Endocrine glands(endocrine, endocrine) - the general name for glands that produce active substances (hormones) and release them directly into the internal environment of the body. The endocrine glands got their name due to the lack of excretory ducts, so the hormones they produce are released directly into the blood. The endocrine glands include the pituitary gland, thyroid gland, parathyroid glands, and adrenal glands.

In addition, there are glands that simultaneously secrete substances into the internal environment of the body (blood) and into the body cavity (intestines) or outside, i.e. performing endocrine and exocrine functions. Such glands, which simultaneously perform both exocrine and intrasecretory functions, include the pancreas (hormones and pancreatic juice involved in digestion), and the gonads (hormones and reproductive material - sperm and egg). However, according to established tradition, these mixed glands are also classified as endocrine glands, collectively combined into the endocrine system of the body. Mixed secretion glands also include the thymus and placenta, which combine the production of hormones with non-endocrine functions.

With the help of hormones produced by the endocrine glands, the body carries out humoral (through body fluids - blood, lymph) regulation of physiological functions, and since all endocrine glands are innervated by nerves and their activity is under the control of the central nervous system, humoral regulation is subordinated nervous regulation, together with which it forms a unified system of neurohumoral regulation.

Hormones are highly active substances. Insignificant amounts of them have a powerful effect on the activity of certain organs and their systems. The peculiarity of hormones is their specific effect on a strictly defined type of metabolic processes or on a specific group of cells.

In some cases, the same cell can be exposed to many hormones, so the final biological result will depend not on one, but on many hormonal influences. On the other hand, hormones can influence any physiological process in direct opposition to each other. So, if insulin lowers blood sugar, adrenaline increases this level. The biological effects of some hormones, in particular corticosteroids, are that they create conditions for the manifestation of the action of another hormone.

According to their chemical structure, hormones are divided into three large groups:

1. proteins and peptides - insulin, hormones of the anterior pituitary gland
2. amino acid derivatives - thyroid hormone - thyroxine and adrenal medulla hormone - adrenaline
3. fat-like substances - steroids - hormones of the gonads and adrenal cortex

Hormones can change the rate of metabolism, affect the growth and differentiation of tissues, and determine the onset of puberty. Hormones influence cells in different ways. Some of them act on cells by binding to receptor proteins on their surface, others penetrate the cell and activate certain genes. The synthesis of messenger RNA and the subsequent synthesis of enzymes change the intensity or direction of metabolic processes.

Thus, the endocrine regulation of the body’s vital functions is complex and strictly balanced. Changes in physiological and biochemical reactions under the influence of hormones contribute to the body's adaptation to constantly changing environmental conditions.

All endocrine glands are interconnected: hormones produced by some glands influence the activity of other glands, which ensures a unified system of coordination between them, which is carried out on the principle of feedback [show] .

Feedback principle: increased secretion of thyroxine by the thyroid gland inhibits the production of thyroid-stimulating hormone from the pituitary gland, which regulates the secretion of thyroxine. As a result, the amount of thyroxine in the blood decreases. A decrease in the amount of thyroxine in the blood leads to the exact opposite effect. In the same way, adrenocorticotropic hormone of the pituitary gland regulates the production of hormones by the adrenal cortex.

The leading role in this system belongs to the hypothalamus, the releasing hormones of which stimulate the activity of the main endocrine gland - the pituitary gland. Pituitary hormones, in turn, regulate the activity of other endocrine glands.

Central regulatory formations of the endocrine system

Hypothalamus - the area of ​​the diencephalon, in its anatomical essence, is not an endocrine gland. It is represented by nerve cells (neurons) - hypothalamic nuclei, which synthesize and secrete hormones directly into the bloodstream of the hypothalamic-pituitary-portal system.

It has been established that the hypothalamus is the leading formation in the regulation of pituitary function with the help of hypophysiotropic hormones, called releasing hormones. Releasing hormones are synthesized and secreted by hypothalamic neurons. In addition, it has been established that the hormones vasopressin and oxytocin, previously considered products of the pituitary gland, are actually synthesized in the neurons of the hypothalamus and secreted by them into the neurohypophysis (posterior pituitary gland), from which they are subsequently secreted into the blood during the necessary periods of the body’s life.

There is an idea of ​​a double mechanism of hypothalamic regulation of the tropic functions of the pituitary gland - stimulating and blocking. However, to date it has not been possible to demonstrate the presence of a neurohormone that inhibits, for example, the secretion of gonadotropins. However, there is evidence indicating the inhibitory effect of melatonin (the pineal gland hormone), dopamine and serotonin on the synthesis of the gonadotropic hormones FSH and LH in the pituitary gland.

A striking illustration of the dual mechanism of hypothalamic regulation of tropic functions is the control of prolactin secretion. It was not possible to isolate and establish the chemical structure of prolactin releasing hormone. The main role in the regulation of prolactin release belongs to the dopaminergic structures of the tuberoinfundibular region of the hypothalamus (tuberohypophyseal dopamine system). It is known that the secretion of prolactin is stimulated by thyrotropin-releasing hormone, the main function of which is to activate the production of thyroid-stimulating hormone (TSH). An inhibitor of prolactin secretion is dopamine, a catecholamine, a precursor to the synthesis of adrenaline and norepinephrine.

Dopamine inhibits the release of prolactin from the lactotrophs of the pituitary gland. Dopamine antagonists - reserpine, aminazine, methyldopa and other substances of this group, deplete dopamine reserves in cerebral structures and cause increased release of prolactin. The ability of dopamine to suppress prolactin secretion is widely used clinically. The dopamine agonist bromocriptine (parlodel, carbegoline, dostinex) has been successfully used to treat functional hyperprolactinemia and prolactin-secreting pituitary adenoma.

It should be noted that dopamine not only regulates the secretion of prolactin, but is also one of the neurotransmitters of the central nervous system.

Pineal gland(pineal body)

The pineal body, or superior cerebral appendage, in mammals is a parenchymal organ arising from the caudal part of the roof of the diencephalon, not in contact with the third ventricle, but connected to the diencephalon by a peduncle, the length of which varies. In humans, the stalk of the body of the epiphysis is short, located directly above the roof of the midbrain.

The pineal body includes three main cellular components: pinealocytes, glia and nerve endings, which are located mainly in the perivascular space near the processes of pinealocytes.

Intensive study of the neural regulation of pineal function has shown that the main regulatory stimuli are light and endogenous rhythm generation mechanisms. Light information is transmitted to the suprachiasmatic nucleus via the retinohypothalamic tract. Axons go from the suprachiasmatic nucleus to the neurons of the paraventricular nucleus, and from the latter to the superior thoracic intermediolateral cell chain, which innervates the superior cervical ganglion. This is the hypothetical way of regulating the functions of the pineal gland. It is believed that the retinohypothalamic pathway initiates a rhythm generation mechanism that acts on the rest of the pathway.

Opinions about the role of the pineal gland in humans are controversial. What is certain is that it is not a vestigial organ that sometimes gives rise to tumors. The pineal gland is thought to be metabolically active throughout much of life and secretes melatonin according to a circadian rhythm; In addition, the pineal gland secretes other substances that have antigonadotropic, antithyroid and antisteroid effects.

Melatonin inhibits the formation of thyrotropin-releasing hormone, thyrotropic hormone (TSH), gonadotropic hormones (LH, FSH), oxytocin, thyroid hormones, thyrocalcitonin, insulin, as well as the synthesis of prostaglandins; reduces sexual excitability and brightens the skin by affecting melanophores.

The pituitary gland, or lower medullary appendage, is located in the middle part of the base of the brain, in the recess of the sella turcica and is connected by a leg to the medulla (with the hypothalamus). It is a gland weighing 0.5 g. It has two main sections: the anterior lobe - the adenohypophysis and the posterior lobe - the neurohypophysis.

Adenohypophysis synthesizes and secretes the following hormones:

• Gonadotropic hormones - gonadotropins (gonads - gonads, "tropos" - place)
  • follicle stimulating hormone (FSH)
  • luteinizing hormone (LH)

  Gonadotropins stimulate the activity of male and female gonads and their production of hormones.

• Adrenocorticotropic hormone (ACTH) - corticotropin - regulates the activity of the adrenal cortex and its production of hormones
• Thyroid-stimulating hormone (TSH) - thyrotropin - regulates the function of the thyroid gland and its production of hormones
• Somatotropic hormone (GH) - somatotropin - stimulates the growth of the body.

  Excessive production of growth hormone in a child can lead to gigantism: the height of such people is 1.5 times the height of a normal person and can reach 2.5 m. If the production of growth hormone increases in an adult, when the growth and formation of the body is already completed, then it develops the disease acrogemaly, in which the size of the arms, legs, and face increases. At the same time, soft tissues grow: lips and cheeks thicken, the tongue becomes so large that it does not fit in the mouth.

  If its production is insufficient at an early age, the child’s growth is inhibited and the disease pituitary dwarfism develops (the height of an adult does not exceed 130 cm). A pituitary dwarf differs from a cretin dwarf (with thyroid disease) in the correct proportions of the body and normal mental development.

• Prolactin is a regulator of fertility and lactation in women

Neurohypophysis accumulates hormones synthesized in the nerve nuclei of the hypothalamus

• Vasopressin controls the reabsorption of water in the renal tubules at a certain level and is one of the factors determining the constancy of water-salt metabolism in the body. Vasopressin reduces urination and also constricts blood vessels, which increases blood pressure.

  Decreased function of the posterior lobe of the pituitary gland causes diabetes insipidus, with the patient excreting up to 15 liters of urine per day. Such a large loss of water requires its replenishment, so patients suffer from thirst and drink large amounts of water.

• Oxytocin - causes contraction of the smooth muscles of the uterus, intestines, gall and bladder.

Peripheral endocrine glands

Thyroid

The thyroid gland is located on the front of the neck, on top of the thyroid cartilage. Its mass is 16-23 g. The thyroid gland produces hormones, which include iodine:

• Thyroxine (T 4) - the main hormone of the thyroid gland - is involved in the regulation of energy metabolism, protein synthesis, growth and development. An increase in the release of this hormone is observed in Graves' disease, when body temperature rises and a person loses weight, despite consuming a large amount of food. His blood pressure rises, tachycardia (increased heart rate), muscle tremors, weakness, and increased nervous excitability appear. In this case, the thyroid gland can increase in volume and protrude on the neck in the form of a goiter.

  With insufficient activity of the thyroid gland, myxedema (mucoedema) occurs - a disease that is characterized by a decrease in metabolism, a drop in body temperature, a slow pulse, and sluggish movements. Body weight increases, the skin becomes dry and swollen. The cause of this disease may be either insufficient activity of the gland itself, or a lack of iodine in food. In the latter case, iodine deficiency is compensated by enlarging the gland itself, as a result of which goiter develops.

  If insufficiency of gland function manifests itself in childhood, then a disease develops - cretinism. Children suffering from this disease are weak-minded and their physical development is delayed.

  Removal of the thyroid gland at a young age causes growth retardation in mammals. Animals remain dwarfs, their differentiation of almost all organs slows down.

• Triiodothyronine (T 3) - no more than 20% is secreted by the thyroid gland. The rest of T 3 is formed by deiodination of T 4 outside the thyroid gland. This process provides almost 80% of the T 3 formed per day. Extrathyroidal formation of T 3 from T 4 occurs in the tissues of the liver and kidneys.
• Calcitonin (does not contain iodine) - produced by parafollicular cells of the thyroid gland. The target organs for calcitonin are bone tissue (osteoclasts) and kidneys (cells of the ascending limb of the loop of Gentle and distal tubules). Under the influence of calcitonin, the activity of osteoclasts in the bone is inhibited, which is accompanied by a decrease in bone resorption and a decrease in the content of calcium and phosphorus in the blood. In addition, calcitonin increases the excretion of calcium, phosphates, and chlorides by the kidneys.

For normal functioning of the thyroid gland, a regular supply of iodine to the body is necessary. In areas where the soil and water contain little iodine, people and animals often experience an enlargement of the thyroid gland - endemic goiter. This goiter is a compensatory adaptation of the body to iodine deficiency. Thanks to the increase in the volume of glandular tissue, the thyroid gland is able to produce sufficient amounts of the hormone, despite the reduced intake of iodine in the body. At the same time, it can increase to large sizes and reach a mass of 1 kg or more. Often the owner of such a goiter feels completely healthy, since endemic goiter is not accompanied by changes in the function of the thyroid gland. In order to prevent endemic goiter in areas where there is little iodine in the environment, potassium iodide is added to table salt.

Parathyroid glands

The parathyroid (parathyroid) glands (PTG) are round or oval shaped bodies located on the posterior surface of the thyroid lobes. Their number is not constant and can vary from 2 to 7-8. Normal parathyroid glands measure 1 x 3 x 5 mm and weigh between 35 and 40 mg. After the age of 20, the mass of the parathyroid gland does not change; in women it is slightly larger than in men.

The parathyroid glands produce parathyroid hormone, which regulates the exchange of calcium and phosphorus in the body. This hormone causes the absorption of calcium in the intestine, its release from the bones and its reabsorption from primary urine in the renal tubules.

Removal or damage to the parathyroid glands leads to muscle spasms, convulsions, and increased excitability of the nervous system. This condition is called tetany. It is explained by a decrease in calcium concentration in the blood. Death from suffocation due to spasms of the respiratory muscles is possible.

Thymus

The thymus gland, or thymus, is one of the mixed glands. Its intrasecretory function is to produce the hormone thymosin, which modulates immune and growth processes. The exocrine function ensures the formation of lymphocytes that carry out cellular immune reactions and regulate the functions of other lymphocytes that produce antibodies.

The thymus gland is located retrosternally, in the upper part of the mediastinum.

Pancreas

The pancreas is also one of the mixed glands. It is located in the abdominal cavity, lies at the level of the bodies of 1-2 lumbar vertebrae behind the stomach, from which it is separated by the omental bursa. The pancreas of an adult weighs on average 80-100 g. Its length is 14-18 cm, width - 3-9 cm, thickness - 2-3 cm. The gland has a thin connective tissue capsule and is covered on the outside with peritoneum. The gland consists of a head, body and tail.

The exocrine function of the pancreas is the secretion of pancreatic juice, which enters the duodenum through the excretory ducts and takes part in the breakdown of nutrients.

The intrasecretory function is performed by special cells located in islands (clusters) not associated with the excretory ducts. These cells are called pancreatic islets (islets of Langerhans). The size of the islets is 0.1-0.3 mm, and the total weight does not exceed 1/100 of the mass of the gland. Most of the islets are located in the tail of the pancreas. The islets are penetrated by blood capillaries, the endothelium of which has fenestrae that facilitate the flow of hormones from the islet cells into the blood through the pericapillary space. There are 5 types of cells in the islet epithelium:

• A-cells (alpha cells, acidophilic insulinocytes) - produce glucagon, with the help of which the process of converting glycogen into glucose occurs. The secretion of this hormone leads to an increase in blood glucose levels.
• B cells (beta cells) - secrete insulin, which regulates blood glucose levels. Insulin converts excess glucose in the blood into animal starch glycogen and lowers blood sugar levels. Under the influence of insulin, the absorption of glucose by peripheral tissues increases, and glycogen is deposited in the liver and muscles.

  Removal or damage to the gland causes diabetes. Lack or absence of insulin leads to a sharp increase in blood sugar and the cessation of its conversion into glycogen. Excess sugar in the blood causes it to be excreted in the urine. A disorder of carbohydrate metabolism leads to disruption of the metabolism of proteins and fats; products of incomplete oxidation of fats accumulate in the blood. With complications, the disease can cause hyperglycemic (diabetic) coma, which causes respiratory distress, weakened cardiac activity, and loss of consciousness. First aid consists of urgently administering insulin.

  An increase in insulin secretion leads to an increase in glucose consumption by tissue cells and the deposition of glycogen in the liver and muscles, a decrease in the concentration of glucose in the blood with the development of hypoglycemic coma.

• D cells (delta cells) - produce somatostatin
• D1 cells (D1-argyrophilic cells) are found in small numbers in the islets; they have dense granules in the cytoplasm containing vasoactive intestinal polypeptide
• PP cells - produce pancreatic polypeptide

In clinical practice, the hormones produced by alpha and beta cells of the pancreas are of greatest importance.

Adrenal glands

The adrenal glands are a paired endocrine organ located in the retroperitoneal space above the upper poles of the kidneys at the level of the Th XI - L I vertebrae. The mass of the adrenal glands of an adult is on average 5-8 g and, as a rule, does not depend on gender and body weight. The development and function of the adrenal cortex is regulated by adrenocorticotropic hormone from the pituitary gland.

The adrenal glands consist of two layers, represented by the cortex and medulla, respectively. The adrenal cortex is divided into zona glomerulosa, zona fasciculata and zona reticularis.

The adrenal glands produce several hormones:

• Hormones of the adrenal medulla - catecholamines: adrenaline, norepinephrine, dopamine, as well as other peptides, in particular adrenomedullin.

  A large amount of adrenaline is released during strong emotions - anger, fear, pain, intense muscular or mental work. An increase in the amount of adrenaline entering the blood causes a rapid heartbeat, narrowing of blood vessels (however, the vessels of the brain, heart and kidneys dilate) and increased blood pressure. Adrenaline increases metabolism, especially carbohydrates, and accelerates the conversion of liver and muscle glycogen into glucose. Under the influence of adrenaline, the muscles of the bronchi relax, intestinal motility is inhibited, and the excitability of the receptors of the retina, auditory and vestibular apparatus increases. Increased production of adrenaline can cause an emergency restructuring of body functions under the influence of extreme stimuli.

  In addition, catecholamines regulate the breakdown of fats (lipolysis) and proteins (proteolysis) when the energy source mobilized from carbohydrate stores is depleted. Under the influence of catecholamines, the processes of gluconeogenesis in the liver are stimulated, where lactate, glycerol and alanine are used to form glucose.

  Along with a direct effect on metabolism, catecholamines have an indirect effect through the secretion of other hormones (GH, insulin, glucagon, renin-angiotensin system, etc.).

  Adrenomedullin - takes part in the regulation of hormonal, electrolyte and water balance in the body, lowers blood pressure, increases heart rate, and relaxes smooth muscles. Its content in blood plasma changes under various pathological conditions.

• Hormones of the adrenal cortex
  • hormones of the zona glomerulosa - mineralocorticoids: aldosterone - regulates salt metabolism (Na +, K +) in the body. An excess causes an increase in blood pressure (arterial hypertension) and a decrease in potassium (hypokalemia), a deficiency causes hyperkalemia, which may be incompatible with life.
  • hormones of the zona fasciculata - glucocorticoids: corticosterone, cortisol - regulate carbohydrate and protein metabolism; inhibit the production of antibodies and have an anti-inflammatory effect, and therefore their synthetic derivatives are widely used in medicine. Glucocorticoids maintain a certain concentration of glucose in the blood, increase the formation and deposition of glycogen in the liver and muscles. Excess or deficiency of glucocorticoids is accompanied by life-threatening changes.
  • zona reticularis hormones - sex hormones: dehyroepiandrosterone (DHEA), dehyroepiandrosterone sulfate (DHEA-s), androstenedione, testosterone, estradiol

With insufficient function of the adrenal cortex and a decrease in hormone production, bronze, or Addison's, disease develops. Its characteristic features are bronze skin tone, muscle weakness, increased fatigue, and susceptibility to infection.

Sex glands

The sex glands - ovaries in women and testes in men - are classified as mixed. Their exocrine function is the formation and release of eggs and sperm, and their intrasecretory function is the production of sex hormones that enter the blood.

Ovaries - female gonads are a paired organ that performs generative and endocrine functions in the body. Located in the pelvic cavity, they have an ovoid shape, length is 2.5-5.5 cm, width - 2-2.5 cm, weight - 5-8 g.

In the ovaries, female reproductive cells (eggs) are formed and mature, and sex hormones are also produced: estrogens, progesterone, androgens, relaxin - softening of the cervix and pubic symphysis in preparation for childbirth, inhibin - inhibits the secretion of FSH and some other polypeptide hormones.

Testicles - male gonads - a paired glandular organ that also performs generative and endocrine functions in the body. Located in the scrotum, in the perineal area. In the testicles, male reproductive cells (spermatozoa) are formed and mature, and the sex hormone is produced - testosterone and in small quantities dihydroepiandrosterone and androstenedione (most of them are formed in peripheral tissues).

Sex hormones - androgens (in men) and estrogens (in women) stimulate the development of reproductive organs (gonads and accessory parts of the genital apparatus), the maturation of germ cells and the formation of secondary sexual characteristics. Secondary sexual characteristics mean those features in the structure and functions of the body that distinguish men from women: skeletal structure, muscle development, distribution of hair, subcutaneous fat, structure of the larynx, timbre of voice, uniqueness of the psyche and behavior.

The effect of sex hormones on various functions of the body is especially clearly manifested in animals during removal of the gonads (castration) or their transplantation.

Of great interest are experiments on the transplantation of gonads: in a previously castrated animal, the sexual characteristics of the sex whose glands are transplanted appear. For example, if a castrated hen is given the gonads of a rooster, she will develop a comb, rooster plumage, and pugnacity. On the contrary, if an ovary is transplanted into a castrated rooster, the comb is reduced and the rooster’s enthusiasm disappears. Such “roosters” take care of the offspring and hatch chicks.

Castration was common in Russia in some religious sects. In Italy until the middle of the 19th century. castration of boys who sang in the church choir was practiced in order to preserve their high timbre of voice.

Regulation of the activity of the endocrine glands. Physiological processes in the body are characterized by rhythm, i.e., regular repetition at certain intervals.

Mammals and humans experience sexual cycles, seasonal fluctuations in the physiological activity of the thyroid gland, adrenal glands, gonads, daily changes in motor activity, body temperature, heart rate, metabolism, etc.

Toxic effect on the endocrine glands. Alcohol and smoking have a toxic effect on the endocrine glands, in particular on the sex glands, on the genetic apparatus and the developing fetus. Children of alcoholics often have developmental defects, mental retardation, and serious illnesses.

Drinking alcohol leads to premature aging, personality degradation, disability and death. The great Russian writer L.N. Tolstoy emphasized that “wine destroys people’s physical health, destroys mental abilities, destroys the well-being of the family and, most terrible of all, destroys the soul of people and their offspring.”

Endocrine glands, or endocrine glands, are those glands that do not have excretory ducts and secrete physiologically active substances (hormones) directly into the internal environment of the body -. Together with the nervous system, the endocrine system ensures the body’s adaptation to environmental conditions. But if the nervous system is structurally rigidly organized, then hormones, moving with the blood, act on all organs and where they can contact specific hormone receptors. If the nervous system carries out its influences almost instantly, then the endocrine system develops its effects on the body more slowly, but their duration can be, unlike the nervous system, very significant.

Hormones are substances of various classes (amino acids and their derivatives, peptides, steroids, etc.), which are usually produced and secreted by specialized glands. Although, for example, many hormones are synthesized in the hypothalamic region of the diencephalon. So the hypothalamus is a neuroendocrine organ. All activities of the endocrine system are under the control of the nervous system, although the nervous system is constantly controlled by the endocrine system.

A substance that is classified as a hormone must meet the following criteria: released from living cells, without violating their integrity; not serve as a source of energy; excreted into the blood in very small quantities; enter directly into the blood; act on target organs through specific receptors.

Some hormones have a direct regulatory effect on some organ, while others may have a programming effect, i.e. at a certain moment they change the cells of any tissues for the entire subsequent period of their life.

Receptors for hormones are proteins. Some of them are located on the outer membrane of the cell, and when a hormone molecule binds to such a receptor, a whole cascade of chemical changes in the cell is triggered, and its state changes. Protein-peptide hormones usually have this mechanism of action. This type of reception is called membrane reception. Another type of reception is nuclear. Hormones with such a reception (for example, steroids) must enter the cell, pass into its nucleus and there influence the genetic apparatus of the cell, inducing or inhibiting the synthesis of some proteins. The effects of hormones with nuclear reception develop slowly, but they persist for a very long time.

Endocrine organs

Endocrine glands are involved in the synthesis of hormones directly into the lymph, intercellular fluid and blood. In other words, these are the environments where hormones secreted by the endocrine glands enter. These organs, as a rule, do not have ducts that open directly into blood vessels. According to the classification, the human endocrine glands (HCG) are divided into:

• Directly endogenous glands. Their main function is exclusively to synthesize special substances - hormones.
• Having additional functions. In addition to secretory work, such organs are also involved in other processes in the human body. Examples include the pancreas, thyroid gland, etc.
• Glandular cells, which are located in various tissues and synthesize active substances. The collection of such individual cells forms a diffuse endocrine system.

Pituitary

The pituitary gland is a lower cerebral appendage connected to the hypothalamus by a thin stalk. The mass of the pituitary gland is about 0.5 g. It is located in a special bony recess - the sella turcica. Anatomically and functionally, the pituitary gland is divided into three lobes: anterior, intermediate and posterior. In the anterior lobe of the pituitary gland, peptide hormones are synthesized and released into the blood, controlling the activity of other endocrine glands.

Hormones of the anterior pituitary gland. Adrenocorticotropic hormone (corticotropin, ACTH) stimulates the activity of the adrenal cortex. In turn, the release of ACTH is controlled by corticoliberin, a peptide produced in the hypothalamus. With an excess of ACTH, Cushing's syndrome develops: the adrenal cortex grows, obesity occurs, headaches, hysteria, etc. appear.

Thyroid-stimulating hormone (TSH) stimulates the synthesis of thyroid hormones. The release of TSH is controlled by thyrotropin-releasing hormone, a peptide produced in the hypothalamus.

Gonadotropins (luteinizing and follicle-stimulating hormones) control the activity of the gonads. They enhance the formation of male and female sex hormones in the testes and ovaries, stimulate the growth of the testes and the growth of follicles. The synthesis and release of gonadotropins is controlled by luliberin, a peptide produced in the hypothalamus.

Somatotropic hormone (growth hormone) does not act on any one endocrine gland, but stimulates the production of tissue growth factors in the cells of many tissues. In turn, these tissue factors stimulate the growth of all parts of the body. With a lack of somatotropic hormone, children develop pituitary dwarfism, and with an excess, pituitary gigantism. If an excess of somatotropic hormone is observed in an adult, when normal growth has already stopped, then a disease occurs - acromegaly, in which the nose, lips, fingers and toes grow. The production of somatotropin is regulated by peptides of the hypothalamus: it is stimulated by somatoliberin and inhibited by somatostatin.

Prolactin stimulates milk production in nursing mothers and is involved in organizing the activity of the gonads.

The intermediate lobe of the pituitary gland produces melanocystimulating hormone, the functions of which have not been sufficiently studied, but its excess has been shown to enhance skin pigmentation and it noticeably darkens.

The hormones of the posterior lobe of the pituitary gland - vasopressin (antidiuretic hormone - ADH) and oxytocin - are peptides and are similar in chemical structure. They are produced in the neurons of the hypothalamus, and then descend along the leg into the posterior lobe of the hypothalamus and from there they can enter the blood. The main functions of vasopressin are to enhance reabsorption in the renal tubules, which leads to a decrease in urine volume. This hormone takes a vital part in regulating the constancy of the internal environment of the body, and when it is deficient, a person develops a disease - diabetes insipidus, in which the body loses a large amount of certain salts. Oxytocin stimulates the contraction of the smooth muscles of the vas deferens and oviducts, and also plays a critical role during childbirth by stimulating the contraction of the muscles of the uterus.

Thyroid

The thyroid gland is located on the anterior wall of the larynx, consists of two lobes and an isthmus and has a mass of 25 to 40 g. The outside of the gland is covered with a connective tissue membrane. The gland itself is formed by special vesicles - follicles, in which hormones containing iodine are produced - thyroxine (tetraiodothyronine) and triiodothyronine. Thyroid hormones perform a number of functions. Firstly, they are programming, participating, for example, in the puberty of various animals and humans. If a frog tadpole is deprived of these hormones, it will grow to gigantic sizes, but will not be able to turn into a frog. Secondly, these hormones increase metabolism, stimulating cellular respiration, and increase the secretion of somatotropic hormone from the pituitary gland. Third, thyroid hormones increase the body's production of heat - thermogenesis. Diseases associated with disorders of the thyroid gland can occur not only due to changes in the gland itself, but also due to a lack of iodine in the body, diseases of the anterior pituitary gland, etc.

When the function of the thyroid gland decreases in childhood, cretinism develops, characterized by inhibition in the development of all body systems, short stature, and dementia. In an adult, with a lack of thyroid hormones, myxedema occurs, which causes swelling, dementia, decreased immunity, and weakness. This disease responds well to treatment with thyroid hormones administered externally. When the activity of the thyroid gland increases, Graves' disease occurs, in which excitability, metabolism, and heart rate increase sharply, and bulging eyes (exophthalmos) and weight loss are characteristic.

In those geographical areas where the water contains little iodine (usually found in the mountains), the population often experiences goiter - a disease in which the secreting tissue of the thyroid gland grows, but cannot synthesize full-fledged hormones in the absence of the required amount of iodine. In such areas, iodine consumption by the population should be increased, which can be ensured, for example, by selling table salt with the obligatory small additions of sodium iodide.

Parathyroid glands

Parathyroid glands are small glands located on the surface or in the thickness of the thyroid gland, usually two on each side. They secrete parathyroid hormone, which regulates calcium metabolism in the body. When these glands are damaged, there is a lack of calcium ions in the blood, convulsions, vomiting and death due to paralysis of the respiratory muscles. With increased function, bones begin to lose Ca 2+, and muscle weakness occurs. At the same time, the level of Ca 2+ in the blood plasma increases.

Pancreas

The pancreas has mixed secretion: some of its cells secrete a number of digestive enzymes through ducts into the duodenum (exocrine), and clusters of other cells called islets of Langerhans secrete the hormones insulin and glucagon directly into the blood. The continuous release of insulin into the blood is necessary so that the main source of energy - glucose - can freely pass from the blood plasma into the tissues, and its excess is deposited in the liver in the form of glycogen polymer. With a lack of insulin, diabetes mellitus develops - a disease in which glucose does not penetrate the tissues, and its level in the blood plasma increases greatly, which entails the removal of glucose from the body in large volumes of urine. If insulin is not administered externally to a diabetic patient, deprivation of the brain of glucose leads to loss of consciousness, convulsions and rapid death. The second hormone of the pancreas - glucagon - is synthesized in special cells of the islets of Langerhans and is necessary for the formation of glucose from glycogen when there is a lack of it in the blood plasma. Thus, insulin and glucagon, having an opposite effect on carbohydrate metabolism, ensure precise regulation of the body's glucose consumption.

Adrenal glands

The adrenal glands are small paired glands located at the upper poles of the kidneys and consisting of two layers: the cortex and the medulla. The cells of the outer cortex produce three groups of hormones:

1) Glucocorticoids, the main one of which is cortisol, stimulate the synthesis of glycogen from glucose, reduce the level of glucose consumption by tissues, inhibit the immune response, and prevent inflammatory processes.

2) Mineralocorticoids (for example, aldosterone) regulate the content of Na + and K + in the body, enhancing the reabsorption of Na + in the renal tubules and stimulating the excretion of K + and H + in the urine.

3) Precursors of sex hormones, mainly male, are involved in the formation of secondary sexual characteristics as programming hormones.

With insufficient functioning of the adrenal cortex, Addison's disease occurs, which is characterized by disturbances in carbohydrate metabolism, low blood pressure, weight loss, nausea, and increased skin pigmentation.

The adrenal medulla produces adrenaline and norepinephrine and is functionally part of a single regulatory system with the sympathetic division of the autonomic nervous system. During periods when the body must work under great stress (in case of injury, during danger, in conditions of increased physical and mental labor, etc.), these hormones enhance muscle work, increase blood glucose levels (to ensure increased energy costs brain), increase blood flow in the brain and other vital organs, increase systemic blood pressure, increase cardiac activity, etc. Thus, hormones of the adrenal medulla serve to ensure the body's response to extreme influences or reactions to stress.

Pineal gland

The pineal gland is a small reddish-brown gland weighing only 0.15-0.20 g, located between the upper tubercles of the quadrigeminal midbrain in a special cavity of the skull. The pineal gland is connected to the brain by a hollow stalk. So far, only one pineal gland hormone is known - melatonin, under the influence of which the release of gonadotropic hormones is inhibited, the rate of puberty changes, and in animals - seasonal physiological cycles are regulated. The work of the pineal gland is sensitive to external light: the synthesis of melatonin in it increases in the dark, and is increased in blind people.

Thymus

The thymus (thymus gland) is a small lymphoid organ, consisting of two lobes and located behind the sternum in the mediastinum. The thymus is well developed only in childhood and practically disappears during puberty. The non-endocrine function of the thymus is that it matures T-lymphocytes necessary to provide immunity, which, after maturation, populate other lymphoid organs. The endocrine function of the thymus is that it releases the peptide hormones thymosin and thymopoietins into the blood, which stimulate the growth and formation of the immune system. If the thymus continues to function actively in an adult, autoimmune diseases may develop, in which, due to a pathological increase in immunity, the destruction of the body's own proteins by antibodies is observed. Such diseases include systemic lupus erythematosus, myasthenia gravis, etc.

Sex glands

Sex glands (gonads) are glands of mixed, that is, both external and internal secretion. The female sex glands - the ovaries - release eggs into the external environment, and the hormones estrogens and progestins into the internal environment. The male gonads - the testes - secrete sperm into the external environment, and androgens into the internal environment.

The ovaries secrete estradiol into the blood, an ovulation inducer related to estrogen, which is also involved in the formation of secondary sexual characteristics of the female type (development of the mammary glands, a certain body type, etc.). Progesterone, a progestin, is produced in the corpus luteum, which forms at the site of a ruptured follicle. Progesterone is a pregnancy hormone; it is necessary for the attachment (implantation) of the embryo to the wall of the uterus, and also inhibits the maturation and ovulation of follicles during pregnancy.

The testes secrete androgens into the blood, the main of which is testosterone, which performs a number of functions. It is necessary for the normal formation of the reproductive system in the embryo according to the male type, for the development of male secondary sexual characteristics (hair growth and muscle development according to the male type, low voice, metabolic and behavioral characteristics, etc.), ensures the constancy of spermatogenesis, etc.

The work of all organs and systems is coordinated by a number of specific internal factors. Thanks to their well-coordinated mechanism, the human body reacts correctly and in a timely manner to the action of stimuli. plays one of the main roles in these processes.

The basis of this system are the intrasecretory glands. What should be classified as endocrine glands, whether the glands of the brain belong to them and what features of their work can be identified - we will consider below.

Endocrine system and its features

The endocrine apparatus is represented by working cells, some of which are localized, forming an organ, while others are in a free, scattered state. The organs that belong to this system are called endocrine glands. The peculiarity of their anatomy is that the excretory ducts, through which the produced secretion flows, open into the body.

The endocrine system performs its function with the help of specific substances produced - hormones. These chemicals represent important functional mechanisms necessary for the adequate functioning of the body as a whole.

Once hormones enter the circulatory, lymphatic systems or cerebrospinal fluid, they begin to act as catalysts. The main functions of the endocrine glands are based on the following processes:

• participation in metabolism;
• coordination of the body’s work and interaction of all its systems;
• maintaining balance when exposed to external stimuli;
• regulation of growth processes;
• control of sexual differentiation;
• participation in emotional and mental activities.

The active substances produced by the endocrine gland system are specific factors, since each of them also performs a specific function. Hormones act in the human body in the presence of the necessary physical and chemical conditions. This occurs depending on the constituent elements of food entering the body and the intermediate stages of metabolism.

Hormones tend to influence the functioning of organs and glands remotely, that is, while being far from the target. Another feature is that changing the temperature does not affect the operation of the active substances.

Glands of the endocrine system

The endocrine glands include the pituitary gland, parathyroid and thyroid glands, pancreas, adrenal glands, ovaries and testes, and pineal gland.

The thyroid gland, adrenal cortex and gonads are considered dependent on the pituitary gland for their work, since pituitary hormones directly affect the work of the glands.

The remaining glands are not tropic, that is, they do not obey the work of the pituitary system.

All endocrine glands are represented here. The table also indicates the location of the organs and the hormones they produce.

Glands of the brain

The endocrine glands include the pituitary gland and the pineal gland. Let's take a closer look at the work of each of them.

The pituitary gland is located in the brain, protected in front by the saddle bones of the skull. This gland is considered the beginning of all metabolic processes occurring in the body. It consists of two parts, each of which produces specific active substances:

• anterior - adenohypophysis;
• posterior - neurohypophysis.

Both lobes are autonomous from each other because they have separate innervation, blood circulation and connections with other parts of the brain.

One part of the pituitary gland constantly produces antidiuretic hormone, or vasopressin. The function of this substance is very important for humans, since it controls fluid balance and the functioning of the kidney tubules. When it enters the bloodstream, the kidneys begin to retain water in the body, and when its amount decreases, they release it to the external environment.

Oxytocin is a “female” hormone, although it is also present in the body of men. Its work is manifested in the ability of the uterine muscles to actively contract, that is, the substance is responsible for adequate labor activity. The same hormone is involved in the processes of removal of placenta in the postpartum period and lactation after childbirth.

The adenohypophysis coordinates the work of some endocrine glands. Which endocrine glands are regulated by the anterior lobe of the pituitary system and with the help of what substances does this happen?

1. The thyroid gland - its work is directly dependent on thyroid-stimulating hormone.
2. Adrenal glands - are regulated by the level of adrenocorticotropic hormone in the blood.
3. Gonads - their work is influenced by FSH and LH.
4. Prolactin is a hormone of the adenohypophysis that affects the functioning of the mammary glands during lactation. Somatotropin is a substance whose task is to coordinate the body’s growth and development, as well as participate in protein biosynthesis.
5. Hormones of the pineal gland (pineal gland) are involved in human regulation, stimulate the immune system, reduce stress and blood pressure, and lower sugar levels.

Thyroid and parathyroid glands

The endocrine glands include the thyroid and parathyroid. They are located in one area - at the level of the middle cartilages of the trachea.

Triiodothyronine and thyroxine are considered iodine-rich active substances. They take part in metabolic processes, regulate the level of glucose absorption by the body's cells and break down fats. Thyroid calcitonin lowers calcium levels in the blood.

The main function of the parathyroid gland and its hormone is based on improving the functioning of the nervous and musculoskeletal systems, which is achieved by increasing the level of calcium in the body and its absorption by cells.

Functional features of the pancreas

This organ belongs not only to the endocrine system, but also to the digestive system. The hormonal function is performed by the so-called glands located in the tail. These islets contain several types of cells that differ in structure and the hormone they produce:

• alpha cells: produce (regulate carbohydrate metabolism);
• beta cells: produce insulin (reduces blood sugar);
• delta cells: secretion of somatostatin;
• epsilon cells: produce the “hunger” hormone ghrelin.

Adrenal glands and their hormones

The gland is represented by an outer layer of cells (cortical part) and an inner layer (brain part). Each part produces its own specific active substances. The cortex is characterized by the production of glucocorticoids and mineralocorticoids. These hormones take an active part in metabolic processes.

Adrenaline is an internal hormone responsible for the functioning of the nervous system. With a sharp increase in its amount in the bloodstream, tachycardia, hypertension, dilated pupils and muscle contraction appear. Norepinephrine is also synthesized by the inner layer of adrenal cells. Its action is aimed at activating the parasympathetic nervous system.

Gonads

The endocrine glands also include the testes and ovaries. The hormones they produce are responsible for the normal functioning of the reproductive system. For women, this is the period of maturation, pregnancy and labor. Male hormones are also responsible for the maturation and appearance of sexual characteristics.

The functions of the endocrine glands are based on direct and feedback connections. The testes and ovaries belong to the group of tropic organs, since their work directly depends on the adenohypophysis.

The most common misconceptions about the activity of the endocrine system

Many people mistakenly believe that all glands found in the human body can be called endocrine.

If you ask the following question: “Do the mammary glands belong to the endocrine glands?”, then the unequivocal answer will follow - no. The mammary glands belong to the group of excretory organs, that is, their excretory ducts open outwards and not into the body. In addition, the mammary glands do not produce hormones on their own.

There will be a negative answer to the following question: “Do the lacrimal glands belong to the endocrine glands?” From a medical point of view, the lacrimal glands, like the mammary glands, do not belong to the organs of the endocrine apparatus, since they do not have the ability to produce hormonally active substances.

Female hormonal diseases. The most effective treatment methods Yulia Sergeevna Popova

ENDOCRINE GLANDS

ENDOCRINE GLANDS

As mentioned above, endocrine glands, or endocrine glands, do not have excretory ducts: their secretion products enter directly into the blood, lymph, or neighboring cells. Therefore, all endocrine glands have a rich blood supply.

Hormones produced by the endocrine glands carry out chemical regulation of the activity of the entire body and have a pronounced effect in minimal quantities. Regulation of the amount of hormones in the body and their effect on various systems and organs occurs very quickly - it is not for nothing that hormonal drugs are one of the most potent agents available to modern medicine. Therefore, under no circumstances should you take hormonal medications without a doctor’s prescription. The optimal balance of these substances in the body is extremely important.

The main glands of the endocrine system are the hypothalamus, pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pineal gland and gonads (testicles in men, ovaries in women).

The central part of the endocrine system consists of the hypothalamus, pineal gland and pituitary gland. The main center that regulates the production of hormones by the endocrine glands and their release into the blood is the hypothalamus, located in the brain. It receives information from the central nervous system and switches it to the pituitary gland.

The pituitary gland regulates the secretion of all endocrine organs dependent on it, which are the peripheral part of the endocrine system (thyroid gland, adrenal cortex, testes and ovaries). The peripheral part of the endocrine system also includes the parathyroid glands, some cells of the pancreatic islets, and hormone-producing cells of other organs.

In turn, the hormones of the endocrine glands have a reverse effect on the hypothalamic-pituitary system. Much about the interaction of these systems remains unexplored, and researchers are intensively studying these issues.

Hypothalamus

The hypothalamus unites the nervous and endocrine systems into the neurosecretory system and is the highest center for the regulation of autonomic functions. In other words, this small section of the brain, weighing only about 5 g, is the very conductor thanks to which all systems of our body function like a harmonious orchestra.

From the surface of the body and internal organs, signals about the state of the body are sent to the hypothalamus. In the medial region of the hypothalamus there are special neurons that perceive information about the most important parameters of blood and cerebrospinal fluid - temperature, water-electrolyte composition of plasma, hormone content in the blood. Through neural mechanisms, the medial region of the hypothalamus controls the activity of the pituitary gland. Thus, this region serves as an intermediate link between the nervous and endocrine systems.

The hypothalamus secretes substances with hormonal activity (the so-called releasing hormones, from English release - release). They have a relatively simple chemical structure and influence the pituitary gland, causing it to secrete various more complex hormones. With excessive release of hormones that activate the pituitary gland, an increase in the function of the thyroid gland and gonads can be observed. This made it possible to use releasing hormones in clinical practice and use them in the diagnosis of certain endocrine diseases. Along with hormones that activate the pituitary gland, the hypothalamus secretes biologically active substances that suppress the production of hormones by the pituitary gland (inhibitors).

Regulation of the activity of our body by the hypothalamus determines all the most complex vegetative and behavioral reactions: thermoregulation, food reflexes, sexual behavior, etc.

The influence of the hypothalamus on sexual functions is associated with its regulation of the activity of the gonads and participation in the organization of the nervous mechanisms necessary for sexual behavior. Regulation of sexual function is carried out through the synthesis and release of gonadotropin-releasing hormones (GC-RG). Unlike the male body, in the female body the release of gonadotropins occurs not only in a tonic (constant) mode, but also in a cyclic (periodic) mode.

In the presence of pathology of the hypothalamic region, malfunctions in the functioning of the reproductive system are observed (for example, menstrual irregularities). In childhood, pathology of the hypothalamus can manifest itself in changes in the timing of puberty.

During intrauterine development of the fetus, the hypothalamus of the unborn child influences the formation of its gender. During puberty, based on a signal coming from the hypothalamus through the pituitary gland, the sex glands begin to intensively produce the corresponding male or female sex hormones, under the influence of which secondary sexual characteristics and erotic experiences appear in the adolescent.

The hypothalamus produces important hormones such as oxytocin and vasopressin. When the production of vasopressin by the cells of the hypothalamus is disrupted, a serious disease develops - hypothalamic diabetes insipidus.

Eating behavior is also associated with the hypothalamus. When the corresponding zone is electrically stimulated, an animal with artificially induced feeding behavior begins to eat, even if it is not hungry, and at the same time chews inedible objects. With lesions of the lateral areas of the hypothalamus, there is aphagia(refusal of food). Destruction of the medial areas of the hypothalamus, on the contrary, is accompanied hyperphagia(excessive food consumption).

However, the areas of the hypothalamus whose stimulation leads to different behavioral responses overlap widely. This means that these processes cannot be considered outside of their interaction (as might be suggested by the existence of such terms as “hunger center” and “satiety center”). To date, the neural organization of the hypothalamus, thanks to which this small formation is able to control many vital behavioral reactions and neurohumoral regulatory processes, remains a mystery and the object of further scientific research.

The pituitary gland is a round formation located on the lower surface of the brain. This organ, which belongs to the central link of the endocrine system, consists of two large lobes, different in origin and structure: anterior - adenohypophysis(accounts for 70–80% of the total mass of the gland) and posterior – neurohypophysis. The intermediate (middle) lobe of the pituitary gland is well developed in many animals, and in humans it is a thin layer of cells between the anterior and posterior lobes. These cells synthesize their specific hormones.

The anterior lobe is the most active. It secretes various hormones: adrenocorticotropic, stimulating the activity of the adrenal cortex; thyroid-stimulating, affecting the functioning of the thyroid gland; gonadotropic hormones affecting the sex glands; prolactin, which stimulates the function of the mammary gland, etc.

Gonadotropic hormones of the pituitary gland stimulate the activity of the ovaries. Three such hormones have been identified: follicle-stimulating(FSH), which promotes the development of ovarian follicles; luteinizing(LH), which causes luteinization of follicles; luteotropic(LTG), which supports the function of the corpus luteum during the menstrual cycle and has a lactotropic effect.

The posterior lobe is much smaller. It does not contain glandular tissue and is very similar in structure to nervous tissue (hence the name “neurohypophysis”). The posterior lobe of the pituitary gland does not secrete hormones; it is a kind of storage facility for them. Vasopressin and oxytocin accumulate here, which are formed in the nuclei of the hypothalamus and from there penetrate into the posterior lobe of the pituitary gland.

Together with the hypothalamus, the pituitary gland forms the hypothalamic-pituitary system, which controls the activity of the peripheral endocrine glands. The size of the pituitary gland is quite individual; on average, in an adult, it varies from 0.5 to 0.7 g.

The activity of the pituitary gland determines: growth processes; protein synthesis; development and function of the mammary glands. It stimulates the growth of ovarian follicles, the production of iodine-containing hormones, and also regulates fat metabolism. Disturbances in the secretion of pituitary hormones cause various disorders in the body, the nature of which depends on the degree and type of damage to the pituitary gland and the associated excess or deficiency of hormone secretion.

Insufficiency of pituitary function in adults can be associated with inflammatory processes in it, sometimes with tumor damage to the pituitary gland, and in women - with blood loss during childbirth. It is manifested by weakness, weight loss, low blood pressure, anemia, as well as endocrine disorders (lack of menstruation, decreased libido, etc.). Prevention of this condition in women is largely related to the prevention of bleeding during childbirth.

This organ has not been studied enough, but currently it is classified as part of the endocrine system. According to recent biological research, the pineal gland, or pineal gland, is part of the photoneuroendocrine system. Light has a blocking effect on its activity, and darkness has a stimulating effect.

The pineal gland of a healthy adult weighs just over 100 mg. This small formation produces hormones melatonin And serotonin. The activity of the pineal gland has a clearly defined daily rhythm: melatonin is synthesized at night, serotonin is synthesized during the day. It is assumed that the cyclical action of these hormones allows the body to navigate and adapt to the cycle of day and night.

The full functional significance of the pineal gland has not yet been determined. Perhaps its activity affects all hypothalamic-pituitary hormones, as well as the immune system. Known functions of the pineal gland include inhibition of sexual development and sexual behavior, as well as tumor growth. Melatonin production is most active in children; upon reaching puberty it decreases.

According to experiments, the drug, which is an extract of melatonin, increases the average life expectancy of animals by 20–25%. It is not surprising that many researchers are showing great interest in this potential “elixir of youth” for humans.

Thyroid

This is the largest endocrine gland. In a healthy adult, its mass is 20–30 g (it decreases with age). The gland gets its name from the thyroid cartilage and does not resemble a shield in any way. This is an unpaired organ located in the neck and consisting of two lobes connected by a narrow isthmus.

The thyroid gland produces hormones involved in the regulation of metabolism and growth processes - thyroxine, triiodothyronine, thyrocalcitonin. They increase the metabolic rate and the level of oxygen consumption by organs and tissues. The biological effect of thyrocalcitonin is to ensure proper calcium metabolism.

The functions of the gland are regulated by the hypothalamus. In turn, thyroid hormones affect the functional state of the anterior pituitary gland. The production of hormones depends on various factors: the activity of other endocrine glands (anterior pituitary gland, adrenal glands, gonads) and the intake of iodine from food. The production of hormones is also affected by environmental temperature and various emotional and physical stimuli.

Thyroid hormones have a wide range of effects on the body. They are essential for the development of the brain and nervous system in children; regulate the maturation of tissues and organs, determining their functional activity, growth and metabolism.

The absence, deficiency, and excess of thyroid hormones lead to various diseases. Insufficiency of gland function may be congenital; At the same time, the fetus, while still in the womb, experiences various metabolic disorders, and the child is born with pronounced changes in the brain. This is the most severe form hypothyroidism, called cretinism. Hypothyroidism is especially common in areas where there is not enough iodine in nature. As a result of the lack of this element, the thyroid gland compensatory increases in order to provide the body with the necessary amount of hormones. When the thyroid gland produces excessive hormones, another disease develops - hyperthyroidism.

Disorders of the thyroid gland and iodine deficiency can also cause mastopathy– a benign disease of the mammary glands, manifested in the proliferation of their tissues.

Parathyroid glands

The parathyroid, or parathyroid, glands are located on the posterior surface of the thyroid gland. There are four of these glands, they are very small, about the size of a pea. Their total mass is only 0.1–0.13 g.

The parathyroid glands produce parathyroid a hormone that regulates the content of salts, calcium and phosphorus in the blood. With its deficiency, the growth of bones and teeth is impaired, and the excitability of the nervous system increases. Many physiological processes (transmission of nerve impulses, blood clotting, bone formation, muscle contraction, egg fertilization, etc.) are carried out only with normal calcium metabolism. Calcium enters the body with food, especially in plant foods.

Lesions of the parathyroid glands may be associated with tumor and inflammatory processes in them. With excessive secretion of parathyroid hormone, it develops hyperparathyroidism, in case of insufficient - hypoparathyroidism.

Pancreas

The pancreas is a very important secretory organ. It is located near the duodenum and is connected to it by a special duct.

This gland belongs to the mixed secretion glands and performs two functions at once - exocrine and intrasecretory. The exocrine function is to secrete digestive enzymes into the duodenum. Intrasecretory - in the production of hormones (insulin, glucagon).

Insulin production occurs in small clusters of cells called pancreatic islets, which are irregularly distributed; each islet has an extensive vascular and nervous network. The main effect of insulin is to lower blood glucose levels. The main effect of glucagon is to increase glucose levels by stimulating its production in the liver. Thus, insulin and glucagon ensure the maintenance of physiological blood glucose levels. When the functions of the pancreas are impaired, diabetes mellitus or the so-called hypoglycemic syndrome develops, manifested by a sharp decrease in blood sugar.

Adrenal glands

The adrenal glands are paired endocrine glands located above the kidneys (hence their name). They play an important role in regulating metabolism, adapting the body to unfavorable conditions and implementing sexual function. These glands consist of two parts - the cortex and the medulla.

The adrenal cortex produces about 50 different hormones, which are divided into three groups: mineralocorticoids, glucocorticoids and sex steroids (androgens and estrogens). Glucocorticoids regulate the secretion of hormones by the thymus gland. For a long time, the thymus was included in the endocrine system, but in recent years most experts are inclined to believe that it does not have a strictly defined endocrine function. The thymus produces soluble thymic (or thymic) hormones that regulate the growth, maturation and differentiation of T cells responsible for our immunity, and also ensure the functional activity of mature cells of the immune system.

The adrenal medulla produces two hormones: adrenalin And norepinephrine. Acting on nerve endings, these hormones regulate the function of the cardiovascular system, influence metabolic processes and participate in the body's adaptive reactions. Epinephrine is considered a metabolic hormone due to its effects on carbohydrate storage and fat mobilization. Norepinephrine constricts blood vessels and increases blood pressure. The adrenal medulla is closely connected to the nervous system.

Adrenal tumors can provoke excessive secretion of certain hormones, leading to masculinization of the female body and feminization of the male body. This is expressed in the appearance of secondary sexual characteristics characteristic of the opposite sex.

The gonads are represented in men by the testes, and in women by the ovaries. The ovaries are paired female reproductive glands located in the pelvic cavity. They perform two functions: endocrine (production of sex hormones) and generative (development of eggs).

The ovaries produce estrogens and a number of other hormones that ensure the normal development of the female genital organs and secondary sexual characteristics, determine the cyclicity of menstruation, the normal course of pregnancy and the performance of other functions of the female body.

The female gonads consist of connective tissue and a cortex in which follicles are located in different stages of development. The follicular apparatus of the ovaries produces mainly estrogens, but also weak androgens and progestins. The corpus luteum of the ovaries (a temporary endocrine gland that exists only in the luteal phase of the menstrual cycle), on the contrary, produces mainly progestins and, to a lesser extent, estrogens and weak androgens.

The human ovaries work cyclically. You will find a detailed description of their activities in the second part of this book. If there are disturbances in the secretion of ovarian hormones, women experience disturbances in sexual development, the menstrual cycle, and may be unable to bear a pregnancy. The most common causes of these pathologies are inflammatory processes in the ovaries, so timely treatment of infections is the prevention of hormonal disorders.

The reproductive system is one of the most delicately balanced and therefore vulnerable systems of our body. At the slightest disruption in hormonal balance, immunity disorders, inflammatory processes, sexually transmitted infections, etc., the woman’s reproductive system, which provides the possibility of conceiving, bearing and giving birth to a child, is the first to suffer. Disorders of the functions of the endocrine glands affect men and women, old people and children equally, but for the female body the flawless functioning of the endocrine system is perhaps of decisive importance.