Hypothalamic pituitary system determines the functional state of the entire endocrine systems s. The anatomical and functional relationship of the hypothalamus and pituitary gland also ensures the unity of the nervous and endocrine systems.

Hypothalamus (hypothalamus) occupies part of the diencephalon downward from the thalamus under the hypothalamic groove and is a cluster nerve cells with numerous afferent and efferent connections. As an autonomic center, the hypothalamus coordinates the function various systems and organs, regulates the function of the endocrine glands (pituitary gland, ovaries, thyroid gland and adrenal glands), metabolism (protein, fat, carbohydrate, mineral and water), temperature balance and the activity of all body systems (vegetative-vascular, digestive, excretory, respiratory, etc. .).

This multifaceted function of the hypothalamus is provided by neurohormones entering it through the portal vascular system after release from the endings of the hypothalamic nerve fibers. Hypothalamic hormones are released in a pulsating manner and control the function of the pituitary gland, and their level, in turn, is determined by the level of peripheral hormones in the blood endocrine glands, reaching the hypothalamus, according to the feedback principle (activation signals when there is a lack of hormones or inhibition when their levels are high).

According to the approved International Nomenclature (1975), hypothalamic releasing hormones are divided according to their functional significance into luliberins and statins (releasing and inhibitory). To date, 10 releasing hormones are known: LHRH - luliberin and FSHRG - foliberin (gonadotropic liberins), CTHRG - corticoliberin, TSHRG - thyrotropin-releasing hormone, STHRH - somatoliberin, PLRH - prolactoliberin, MSHRH - melanoliberin, SIRG - somatostatin, Germany - prolactostatin and MIFRG - melanostatin.

In total hypothalamic neurons secrete about 40 compounds, many of which act as synaptic modulators or mediators of the neurosecretory function of the hypothalamus. In particular, vasopressin, oxytocin, and neurophysin are localized in it. At the same time, the biosynthesis of biologically active peptides occurs not only in the hypothalamus. Thus, STHRH is formed in the pancreas, intestinal mucosa and in cerebral neurosecretory cells, and TSHHRH is produced in other parts of the central nervous system.

Gonadotropin- releasing hormones (LHRH and FSHHR) of a polypeptide nature (decapeptide) are not isolated separately. They stimulate the pituitary gland to secrete gonadotropic hormones that affect the ovaries, which is accompanied cyclical changes in the target genital organs. Luliberin (LHRH) has been synthesized for clinical application. It induces puberty, libido, potency, ovulation or spermatogenesis. Luliberin has a pronounced effect on the sexual behavior of animals, affecting the sexual centers of the central nervous system.

Corticotropic releasing hormone (CTHRH)- corticoliberin is localized mainly in the posterior lobe of the hypothalamus and regulates the function of the adrenal cortex and is used in clinical practice.

TSHRG - thyrotropin-releasing hormone (TL), providing pronounced action on the release of ACTH, also promotes the release of lipotropin, melanocyte-stimulating hormone and endorphins. It is highlighted in pure form and synthesized, has a pronounced TSH-releasing effect, actively influences behavioral reactions, enhances motor activity, exhibits depressive effects. Along with hormonal effects, TL also acts as a neurotransmitter. Thyroliberin affects the secretion of prolactin and stimulates the release of growth hormone. Using a test with thyrotropin-releasing hormone, differential diagnosis forms of hypothyroidism of primary and secondary origin, various reasons galactorrhea, Itsenko-Cushing's disease.

Growth hormone releasing hormone (GHRH)- somatoliberin, along with other functions, regulates the production and release of growth hormone.

Prolactin releasing hormone (PRLRH)- prolactoliberin (PL) stimulates the secretion of prolactin by the pituitary gland. Found in the median eminence, anterior hypothalamus and extrahypothalamic structures. The chemical nature has not been established and the question of its use has not been finally resolved.

Melanocyte-stimulating releasing hormone (MSHRH)- melanoliberin (ML) affects the function of the anterior and intermediate lobes of the pituitary gland, where the gene for the production and release of this hormone or proopiomelanocortin (POMC) is expressed in various tissues (brain, placenta, lungs, gastrointestinal tract, etc.) in various variants.

Prolactininhibiting releasing hormone (PRLIH-RG) prolactostatin (PRLS) is a hypothalamic peptide factor with prolactininhibiting properties (PIF) and a structure that has not been fully elucidated. Regulation of the synthesis and secretion of prolactin is carried out by hypothalamic agents. Dopamine inhibits the synthesis and secretion of prolactin. IN recent years a new polypeptide was discovered that has both gonadol-berin and prolactostatic activity.

It is called GnRH associated peptide (GATT) with potent prolactin secretion inhibiting properties. Perhaps this is prolactostatin. The inhibition of PRL release is influenced by somatostatin, which inhibits the release activity of thyrotropin-releasing hormone.

Somatoinhibitory releasing hormone (SIHRH)- somatostatin is found not only in the hypothalamus, but also in other parts of the nervous system, as well as in peripheral tissues (pancreas, gastrointestinal tract). In addition to inhibiting the secretion of growth hormone, somatostatin inhibits the release of TSH, prolactin, insulin and glucagon.

Melanocyte inhibitory releasing hormone (MIHR) regulates the function of the intermediate lobe of the pituitary gland.

Pituitary it is reasonably considered the main gland that produces a number of hormones that directly affect the peripheral glands. It is located in the pituitary fossa of the sella turcica sphenoid bone and through the leg it is connected to the brain. The blood supply is carried out in such a way that the blood passes through the median eminence of the hypothalamus, is enriched with releasing hormones and enters the adenohypophysis. Glandular cells produce a number of peptide hormones that directly regulate the function of peripheral glands. It is divided into an anterior lobe - the adenohypophysis and a posterior lobe - the neurohypophysis. The intermediate (middle) part of the pituitary gland consists of large secretory active basophilic cells.

The anterior lobe produces adrenocorticotropic (ACTH), thyroid-stimulating (TSH), luteinizing (LH) and follicle-stimulating (FSH), lipotropic (LiH), somatotropic (GH) hormones and prolactin (PRL). In the intermediate lobe there is melanocyte-stimulating hormone (MSH), in the posterior lobe there is vasopressin and oxytocin. Previously, all hormones were studied separately. New studies of the mechanism of synthesis and intracellular mediators of their action have made it possible to combine these hormones into three general groups: 1) glycoprotein hormones; 2) peptides of the proopiomyelocortin family and 3) a group including growth hormone, prolactin and human chorionic somatom-motropin.

The most complex of the pituitary hormones- these are glycoprotein hormones (TSH, LH, FSH). This group also includes chorionic gonadotropin (CG), a placental hormone.

All of them have a multifaceted impact on various pathological processes, but have structural similarities. They interact with cell surface receptors and activate adenylate cyclase, increasing the level of cAMP, which is their intracellular mediator. All hormones of this group were formed on the basis of a common precursor gene, which gave rise to two subunits: the first, which determines interspecies differences, and the second, which determines the differences between hormones. A feature of glycoprotein hormones is the glycosylation of their molecules.

Hormone molecules are synthesized as preprohormones, which undergo further changes in the cell with the formation of glucosylated proteins.

Gonadal otropins (FSH, LH, HCG) provide gametogenesis and steroidogenesis. FSH-follitropin binds to specific membrane receptors of target tissues (follicular cells of the ovaries and Sertoli cells in the testes).

After activation of adenylate cyclase under the influence of FSH, the level of cAMP increases. At the same time, the growth of follicles is activated, their sensitivity to the action of LH, which induces ovulation, increases, and the secretion of estrogen increases. FSH is secreted cyclically with a peak before or during ovulation (peak is a 10-fold increase in basal level).

Luteinizing hormone (lutropin, LH) stimulates the formation of progesterone by corpus luteum cells and testosterone by Leydig cells. 2a-hydroxycholesterol is first formed from cholesterol. Long term exposure LH leads to desensitization of the receptors of this hormone, which are less sensitive compared to FSH receptors.

The peak of LH secretion in the middle of the cycle induces ovulation in women. Further LG supports the function corpus luteum and progesterone production. After fertilization and implantation of the egg, the LH function passes to the placental hormone - chorionic gonad otropin (CG).

During the first 6-8 weeks, pregnancy is supported by the corpus luteum, then the placenta itself produces progesterone in the amount necessary for pregnancy, while maintaining hCG production. In the interstitial cells of non-hormonal ovarian tissues, LH can induce the formation of a number of androgens and their precursors (androstenedione, dihydroepiandrosterone, testosterone). According to recent data, it is believed that polycystic ovarian syndrome (Stein-Leventhal syndrome) is characterized by increased LH levels, increased androgen products, decreased fertility, increased body weight, and increased growth of body and facial hair.

It is assumed that this syndrome is caused by hyperactivity of the ovarian struma.
Human chorionic gonadotropin is a glycoprotein synthesized by syncytiotrophoblast cells of the placenta, similar in structure to LH. A special increase in the level of the hormone is observed after implantation, so its determination is the basis of many methods for diagnosing pregnancy.

The secretion of FSH and LH is regulated by steroid sex hormones classic scheme negative feedback. The release of LH and FSH is determined by GnRH-gonadotropin-releasing hormone, and the latter by testosterone, estradiol and endorphin.

Thyroid-stimulating hormone (TTT, thyrotropin)- a glycoprotein that, by increasing the amount of cAMP, ensures the biosynthesis of thyroid hormones (T3, T4), concentration and organization of iodide, condensation of iodothyronines and hydrolysis of thyroglobulin. These processes occur within a few minutes. The long-term effects of TSH in the thyroid gland determine the synthesis of proteins, phospholipids and nucleic acids, an increase in the size and number of thyroid cells (which is associated with the formation of T and T4).

The secretion and release of TSH is in turn regulated by thyroid hormones (T3 and T4) and hypothalamic thyrotropin-releasing hormone.

Hormones of the peptide-proopiomelanocortin (POMC) family are represented by a group of active substances that act either as hormones or as neurotransmitters or neuromodulators. POMC peptides are divided into three groups: 1) ACTH, from which melanocyte-stimulating hormone (a-MSH) and corticotropin-like peptide can be formed; 2) P-lipotropin f-LPG), which serves as a precursor to a-lipotropin, p-MSH, a-, (3-, y-endorphins; 3) y-MSH.

POMC is synthesized in 50% of the cells of the anterior pituitary gland and in all cells of the intermediate lobe, but the regulation of this process varies among the lobes. In the anterior lobe, the release of POMC is regulated by corticoliberin and inhibited by glucocorticoids, which suppress the secretion of ACTH. Corticoliberin does not affect the intermediate lobe. The release of POMC in the intermediate lobe is stimulated by serotonin and beta-adrenergic agents (the dopamine agonist ergocryptine) and inhibited by the dopamine antagonist haloperidol.

In other tissues, the regulation of POMC biosynthesis and release is not well understood. Glucocorticoids, corticoliberin, adrenalectomy and hypophysectomy do not affect these processes. Stress reduces the release of beta-endorphin from the hypothalamus, and estrogens increase the release of beta-endorphin from the hypothalamus.

Adrenocorticotropic hormone (ACTH)- a polypeptide that regulates the growth and function of the adrenal cortex. It has interspecific identity. In particular, out of 39 amino acids, peptides have 24 different types are identical, which is widely used for diagnosis and treatment. ACTH increases the synthesis and secretion of adrenal steroids, increasing the conversion of cholesterol to pregnenolone (the precursor to all adrenal steroids). Long-term use ACTH leads to excessive formation of glucocorticoids, mineral ocorticoids and dehydroepidresterone - a precursor of androgens. By exhibiting a trophic effect, ACTH increases protein and RNA synthesis

This occurs due to an increase in cAMP levels after contact of ACTH with plasma membrane receptors, which leads to activation of adenylate cyclase. In fat cells, ACTH activates lipase and enhances glycolysis, which is carried out with the participation of calcium. IN large doses ACTH also stimulates insulin secretion in the pancreas. Regulation of the formation of ACTH from the protein - the precursor of POMC and its secretion is carried out according to the principle of feedback by glucocorticoids and corticoliberin. The integrating role is performed by the central nervous system with the help of neurotransmitters (norepinephrine, serotonin, acetylcholine). It is they who mediate the stress response from ACTH by stimulating glucocorticoids, which are necessary for adaptation of such influences as surgery, hypoglycemia, physical or emotional trauma, effects of cold and pyrogens.

Endorphin peptides are contained in the pituitary gland in an acetylated (inactive) form. In the central nervous system they are present in an unmodified (active) form and act as neuromodulators or neuroregulators. They bind to the same receptors as morphine opiates.

Melanocyte-stimulating hormone (MSH) activates melanogenesis. Three types of MSH are contained in POMC. With low levels of glucocorticoids (Addison's disease), increased skin pigmentation is observed, which is associated with increased activity MSH is present in plasma, although no MSH has been detected in humans after birth.

Group of hormones - growth hormone (GH), prolactin (PRL), chorionic somatomammotropin and placental lactogen (CS, PL) are homologous in structure. Human GH and cholesterol are 8-5% homologous, GH and PRL are 3-5% homologous. They also have lactogenic and growth-stimulating activity.

They are produced only by certain tissues: GH and PRL - by the anterior lobe of the pituitary gland, CS - by syncytiotrophoblastic cells of the placenta. They are secreted according to their own regulatory mechanism. There are several genes on chromosome 17 for GR and PS and one for PRL on chromosome 6.
The growth regulation system is represented by the main links - somatoliberin and somatostatin, as well as insulin-like growth factor (IGF-1), which is formed in the liver. IGF-1 regulates GH secretion by inhibiting the release of somatoliberin and stimulating the release of somatostatin. GH is necessary for postnatal growth and for the normalization of carbohydrate, lipid, nitrogen and mineral metabolism. GH stimulates the transport of amino acids into muscle cells, protein synthesis and reduces the content of amino acids and urea in plasma and urine. All this is accompanied by an increase in the level of RNA and DNA synthesis in individual tissues. On carbohydrate metabolism GH has the opposite effect than insulin. With long-term administration of GH, there is a risk of diabetes mellitus. GH affects mineral metabolism, stimulating bone growth and cartilage formation.

This hormone also has the properties of PRL, promotes the development of mammary glands and actogenesis.

Prolactin (PRL) is a lactogenic hormone, mammotropin and luteotropic hormone) secreted by lactophores - acidophilic cells of the anterior pituitary gland. PRL production is controlled by prolactostatin, which is similar in structure to dopamine. Some believe that dopamine is prolactinin inhibitory factor (PIF). The presence of prolactoliberin is considered doubtful. PRL levels increase during pregnancy, stress, sexual contacts and during sleep, the hormone promotes the initiation and maintenance of lactation.

Chorionic somatomammotropin (CS: placental lactogen) exhibits actogenic and luteotropic activity, and is similar in metabolic effects to GH. CS supports the growth and development of the fetus. It is synthesized by syncytiotrophoblast cells, but it belongs to this group due to the similarity of structure and nature of action with PRL and GR.

Posterior pituitary gland contains two active hormones - vasopressin and oxytocin. Vasopressin (otherwise known as antidiuretic hormone - ADH) is capable of increasing blood pressure and stimulating the reabsorption of water in the distal renal tubules. The specific effect of the second hormone, oxytocin, is to accelerate labor due to increased contractions of the uterine muscles. Both hormones are formed in the hypothalamus, then transported by axonplasmic current to the nerve endings of the posterior lobe of the pituitary gland, from which they are secreted into the bloodstream upon appropriate stimulation, bypassing the blood-brain barrier. ADH is synthesized mainly in the supraoptic nucleus, oxytocin - in the paraventricular nucleus. Both are carried by a specific carrier protein, neurophysin types I and II. Both hormones have a short half-life (2-4 minutes). Their metabolism is carried out in the liver. Many factors that promote the release of oxytocin release prolactin, so oxytocin is considered a prolactin-releasing factor.

Main effect of ADH- an increase in plasma osmolality, which is mediated by osmoreceptors in the hypothalamus to baroreceptors in the cardiovascular system. The release of ADH is regulated by many factors (hemodilution, emotional and physical stress, blood pressure levels).

Adrenaline, like ethanol, suppresses the secretion of ADH. The target organ for ADH is the kidney (cells of the distal convoluted tubules and collecting ducts of the kidneys).

Basic physiological and pharmacological property Oxytocin is the ability to cause contractions of the smooth muscles of the non-pregnant, pregnant uterus and especially during childbirth. An increase in the frequency, intensity and duration of contractions is associated with a decrease membrane potential cells The effectiveness of the hormone dose is determined by the functional state of the uterus (non-pregnant, pregnant in different terms). In the last 4 weeks of pregnancy, the sensitivity of the uterus to oxytocin increases many times, although individual differences are noted. Oxytocin It also has a second property - the ability to cause contractions of the myoepithelial elements of the alveoli of the small ducts of the mammary gland, i.e. promotes the lactation process, improving the movement of milk secreted under the influence of prolactin into the large ducts and milk sinuses.

Diseases associated with pathology of the hypothalamic-pituitary system are the most numerous in endocrinology and are specific for each hormone. Insufficiency or absence of GH caused by panhypopituitarism is especially dangerous in children, as it impairs their ability to normal growth and lead to various types dwarfism An excess of this hormone leads to the development of gigantism, and in adults - to acromegaly.

Low level glucocorticoids leads to the development of Addison's disease. Excessive formation of ACTH by the pituitary gland or its ectopic production is manifested by Itsenko-Cushing syndrome with many metabolic disorders: negative nitrogen, potassium and phosphorus balance; sodium retention, often accompanied by increased blood pressure and the development of edema; impaired glucose tolerance or diabetes mellitus; increased levels of fatty acids in plasma; eosinopenia, lymphocytopenia with an increase in the number of polymorphonuclear leukocytes. The absence of ACTH due to a tumor or infection of the pituitary gland causes the opposite conditions.

Long-term increase in PRL secretion leads to the development of persistent galactorrhea-amenorrhea syndrome. This can also occur with a normal level of PRL in the blood serum, but with an excessively high level of PRL in the blood serum. biological activity. In men, hypersecretion of PRL is accompanied by the development of impotence, gynecomastia with galactorrhea. Chronic overproduction of PRL can be the main pathogenetic link in an independent hypothalamic-pituitary disease, as well as a consequence of a number of endocrine and non-endocrine diseases with secondary involvement of the hypothalamic-pituitary system.

Impaired secretion or action of ADH lead to diabetes insipidus with the release of large volumes of diluted urine. In hereditary nephrogenic diabetes insipidus, ADH levels may be normal, but target cells do not respond to it. The syndrome of excessive secretion of ADH develops with ectopic production of the hormone by various tumors (usually lung tumors) and is accompanied by urinary retention under conditions of hypoosmolality with stable and progressive hyponatremia and increased content sodium in urine.

Empty sella syndrome (TSS) defines various nosological forms, a common feature of which is the expansion of the subarachnoid space into the intersellar region with an enlarged sella turcica. PTS syndrome may develop secondarily after surgical interventions and primarily without them. The syndrome can be asymptomatic (incidental findings) or with a variety of clinical manifestations (headaches, blurred vision, hyperprolactinemia, etc.).

Pathology of the hypothalamic-pituitary region also leads to various gynecological diseases(amenorrhea, neuroendocrine syndromes). Thus, with panhypopituitarism, Sheehan's syndrome can develop, when in the absence of the pituitary level of regulation the function of all peripheral endocrine glands is disrupted, or Simmonds' disease - hypothalamic-pituitary cachexia syndrome.

HYPOTHALAMIC-PITITUITARY SYSTEM- a functional complex consisting of the hypothalamic region of the diencephalon and the pituitary gland.

Main functional value hypothalamic-pituitary system - regulation of the autonomic functions of the body. From the side of the hypothalamus, it is carried out by the paraadenopituitary pathway, bypassing the adenohypophysis, and by the transadenopituitary pathway through the adenohypophysis, when autonomic functions are regulated through a complex of peripheral, endocrine target glands dependent on the pituitary gland. There is also a parapituitary, purely neuroconducting pathway, realized through the system of efferent central neurons of the brain stem and spinal cord, peripheral sympathetic and parasympathetic neurons.

Significant contribution to the study of the morphology, physiology and pathology of G.-g. With. contributed by domestic scientists N. M. Itsenko, L. Ya. Pines, N. I. Grashchenkov and foreign researchers S. Ramon y Cajal, X. Cushing, R. Greving, E. Scharrer, Sentagotai (J. Szentagothai), etc.

G.-g. With. formed by two genetically different parts - the hypothalamus (see) and the pituitary gland (see).

With age, involutional changes are observed, expressed by a decrease in the number of neurosecretory cells of the hypothalamus and pituitary gland, their partial pyknosis (see), changes in the distribution of tigroid substance, various changes in nerve cells, which leads to a decrease in secretory activity.

According to some authors, the main structural and functional components of G.-g. With. There are two types of nerve cells: neurosecretory cells that produce peptides (peptidergic neurons) and cells that secrete monoamines (monoaminergic neurons). Neurosecretory cells that produce peptide neurohormones form magnocellular nuclei: supraopticus (nucleus supraopticus), periventricular (nucleus paraventricularis) and posterior (nucleus post.) nuclei.

Homopositive cells are the largest elements in the hypothalamus, sometimes multinucleated, giant, therefore the neurosecretory formations are called large-cell centers (nuclei), in contrast to the rest of the small-cell nuclei of the hypothalamus. The neurosecretion produced by these cells is stained with chromium hematoxylin or paraldehyde fuchsin using the Gomori method and is called homopositive. Electron microscopy is detected in the bodies and processes of these cells, but especially in the nerve endings (terminals) of axons in the form of elementary granules of two sizes: 100-150 nm (1000-1500 A) and 150-300 nm (1500-3000 A). Neurosecretion, synthesized in the neuroplasm (perikarya) of neurosecretory cells, moves with the current of neuroplasm to the terminal sections of the processes. The bulk of the granules enters the posterior lobe of the pituitary gland. Here, the terminal sections of the axons of neurosecretory cells (neurosecretory endings) form contacts with the capillaries.

Thanks to large cluster endings of axons and capillaries in the neurohypophysis, this part of the hypothalamic-pituitary neurosecretory system is called the neurohemal organ.

However, in modern neuroendocrinology the prevailing opinion is that the neurosecretory formations of the hypothalamus are represented not only by homopositive cells, which are cholinergic and produce octopeptide neurohormones (vasopressin and oxytocin). Along with the homo -power cells of the front hypothalamus, the second group is made up of small neurosecrething cells of adrenergic nature, localized in the mediobasal hypothalamus (adenohypyphysotropic zone) and forming fuzzy limited nuclei: anterior hypothalamic (nucleus hupothalamicus ant Cleus superchiasmaticus) nuclei and bell zone (Zona Praeopticus) ; arcuate, or infundibular (nucleus arcuatus, nucleus infundibularis), periventricular nuclei (nuclei periventriculares, anr. et post.), ventromedial (nucleus ventromedialis) and dorsomedial (nucleus dorsomedialis) nuclei. They produce oligopeptide hormones (see Hypothalamic neurohormones). Their secretion (releasing hormones) is regulated mainly by the ratio of the concentrations of norepinephrine, acetylcholine and serotonin in the hypothalamus.

A common morpho-functional feature of all parts of the neurohypophysis is that in them, on numerous capillaries, the terminals of neurosecretory peptidergic, adrenergic and, according to some researchers, also cholinergic fibers end. The glial stroma of the neurohypophysis is represented by pituicytes (neuroglial cells), which provide trophism to nerve fibers and their terminals; the ability of these cells to phagocytosis is described, in particular, the absorption of metabolic products by these cells is noted.

Blood circulation G.-g. With. is represented by a rich network of capillaries formed by the anterior and posterior pituitary arteries from the arterial circle of the brain (see Pituitary gland).

Functional status information visceral organs and the internal environment of the body, as well as about the changes occurring during external environment, respectively, comes from intero- and exteroceptors mainly to the centers of the midbrain, in particular to the reticular formation, and from there to the hypothalamus. Fine integration of the vegetative functions of the body is carried out by the higher departments of the c. n. with., for example, the limbic system. From all of these parts of the brain, impulses travel through numerous conductors to neurosecretory cells. All neurosecretory peptidergic cells represent the final efferent link in the implementation of nervous influences on the activity of the adenohypophysis and visceral organs, including endocrine target glands.

Feedback connections play an important role in neuroendocrine relationships, among which there are “short” connections (adenopituitary gland - hypothalamus) and “long” connections (target glands - hypothalamus). Thanks to these connections, self-regulation of the neuro-endocrine complex occurs within the whole organism. Thus, the regulatory influence of both triple hormones of the adenohypophysis and hormones of the peripheral glands is allowed on the intensity of production in the perikarya of neurosecretory cells and the release of adenohypophysiotropic, and, possibly, also viscerotropic peptide neurohormones from the terminals of their axons.

The considered unity of the hypothalamus-pituitary complex is clearly manifested in its pathology. This is expressed in the difficulty of differentiating the localization of patol processes (in the hypothalamus or pituitary gland).

Bibliography: Aleshin B.V. Hyotophysiology of the hypothalamic-pituitary system, M., 1971, bibliogr.; Voitkevich A. A. Neurosecretion, L., 1967, bibliogr.; Polenov A. L. Hypothalamic neurosecretion, L., 1971, bibliogr.; Polenov A. L. and Belenky M. A. On some patterns of formation of the neurohemal sections of the hypothalamic-pituitary neurosecretory system in the onto- and phylogenesis of vertebrates, Zhurn, evolyuts, biokhim, i fiziol., vol. 9, no. 4, p. 355, 1973, bibliogr.; Tonkikh A. V. Hypothalamic-pituitary region and regulation physiological functions organism, M.-L., 1965, bibliogr..; Aspects of neuroendocrinology, ed. by W. Bargmanna. B. Scharrer, Heidelberg-N.Y., 1970; Bargmann W. Neurosecretion, Int. Rev. Cytol., v. 19, p. 183, 1966, bibliogr.; Scharrer E. a. Scharrer B. Neuroendocrinology, N. Y.-L., 1963, bibliogr.

B.V. Aleshin, A.L. Polenov.

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The hypothalamic-pituitary system belongs to vital role in regulating the activity of all endocrine glands. Many cells of one of the vital parts of the brain, the hypothalamus, have the ability to secrete hormones called releasing factors. These are neurosecretory cells, the axons of which connect the hypothalamus with the pituitary gland. The hormones secreted by these cells, entering certain parts of the pituitary gland, stimulate the secretion of its hormones. The pituitary gland is a small oval-shaped formation located at the base of the brain in the recess of the sella turcica of the main bone of the skull.

There are anterior, intermediate and posterior lobes of the pituitary gland. According to the International Anatomical Nomenclature, the anterior and intermediate lobes are called the adenohypophysis, and the posterior lobe is called the neurohypophysis.

Under the influence of releasing factors, triple hormones are released in the anterior lobe of the pituitary gland: somatotropic, thyroid hormone, adrenocorticotropic, gonadotropic.

Somatotropin. or growth hormone, causes bones to grow in length, accelerates metabolic processes, which leads to increased growth and increased body weight. The lack of this hormone manifests itself in short stature (height below 130 cm), delayed sexual development; the proportions of the body are preserved. The mental development of pituitary dwarfs is usually not impaired. Among the pituitary dwarfs there were also outstanding people.

Excess growth hormones in childhood leads to gigantism. The medical literature describes giants with a height of 2 m 83 cm and even more (3 m 20 cm). Giants are characterized by long limbs, lack of sexual function, and reduced physical endurance.

Sometimes excessive release of growth hormone into the blood begins after puberty, i.e., when the epiphyseal cartilages have already ossified and growth tubular bones in length is no longer possible. Then acromegaly develops: the hands and feet, the bones of the facial part of the skull enlarge (they ossify later), the nose, lips, chin, tongue, ears grow rapidly, vocal cords thicken, causing the voice to become rough; the volume of the heart, liver, and gastrointestinal tract increases.

Adrenocorticotropic hormone (ACTH) influences the activity of the adrenal cortex. An increase in the amount of ACTH in the blood causes hyperfunction of the adrenal cortex, which leads to metabolic disorders and an increase in the amount of sugar in the blood. Itsenko-Cushing's disease develops with characteristic obesity of the face and trunk, excessively growing hair on the face and trunk; Often at the same time, women grow a beard and mustache; blood pressure increases; bone tissue loosens, which sometimes leads to spontaneous bone fractures.

The adenohypophysis also produces a hormone necessary for normal function thyroid gland (thyrotropin).

Several hormones of the anterior pituitary gland influence the functions of the gonads. These are gonadotropic hormones. Some of them stimulate the growth and maturation of follicles in the ovaries (folitropin) and activate spermatogenesis. Under the influence of lutropin, women undergo ovulation and the formation of the corpus luteum; in men, it stimulates testosterone production. Prolactin affects milk production in the mammary glands; with its deficiency, milk production decreases.

Of the hormones of the intermediate lobe of the pituitary gland, the melanophore hormone, or melanotropin, which regulates color, is the most studied skin. This hormone acts on skin cells containing pigment grains. Under the influence of the hormone, these grains spread throughout all processes of the cell, as a result of which the skin darkens. With a lack of the hormone, colored pigment grains accumulate in the center of the cells, and the skin turns pale.

During pregnancy, the content of melanophore hormone in the blood increases, which causes increased pigmentation of certain areas of the skin (pregnancy spots).

Under the influence of the hypothalamus, the hormones antidiuretin, or vasopressin, and oxytocin are released from the posterior lobe of the pituitary gland. Oxytocin stimulates the smooth muscles of the uterus during childbirth. It also has a stimulating effect on the secretion of milk from the mammary glands.

The hormone of the posterior lobe of the pituitary gland, called antidiuretic (ADH), has the most complex effect; it enhances the reabsorption of water from primary urine, and also affects the salt composition of the blood. When the amount of ADH in the blood decreases, diabetes insipidus occurs ( diabetes insipidus), in which up to 10-20 liters of urine are separated per day. Together with the hormones of the adrenal cortex, ADH regulates water-salt metabolism

in the body.

The structure and function of the pituitary gland undergo significant changes with age. In a newborn, the mass of the pituitary gland is 0.1-0.15 g; by the age of 10 it reaches 0.3 g (in adults, 0.55-0.65 g).

Temperament and personality
Personality and temperament are interconnected in such a way that temperament acts as a common basis for many other personal properties, especially character. However, it only determines the dyne...

The unity of nervous and hormonal regulation in the body is ensured by the close anatomical and functional connection of the hypothalamus and.

Hypothalamic-pituitary system determines the state and functioning of the majority either through the endocrine axes: hypothalamus -> pituitary gland -> peripheral glands (thyroid, adrenal glands, testes or ovaries), or through the ANS: hypothalamus -> ANS centers of the trunk and spinal cord -> ANS ganglia -> endocrine glands and their vessels.

The pituitary gland (pituitary gland) is located below the hypothalamus in the sella turcica of the sphenoid bone of the skull base and consists of the anterior (adenohypophysis) and posterior (neurohypophysis) lobes. The intermediate lobe is rudimentary in an adult. The mass of the pituitary gland is only 0.5-0.9 g. With the help of a stalk, the neurohypophysis is anatomically connected to the hypothalamus. The axons of magnocellular neurons of the supraoptic (SON) and paraventricular (PVN) nuclei approach the cells of the neurohypophysis. The adenohypophysis is connected to the hypothalamus through the portal (portal) system of the superior pituitary artery. The blood flow in the portal system is directed from the hypothalamus to the adenohypophysis. On the vessels of the median eminence of the pituitary stalk, small cell neurons of the hypothalamus form axovasal synapses, through which they release hormones into the blood that control the endocrine functions of the pituitary gland. The production of hormones by the pituitary gland is also regulated by the ANS.

Rice. Diagram of the hypothalamic-pituitary system

Functions of the hypothalamic-pituitary system

Part - the hypothalamus - and the pituitary gland extending from its base anatomically and functionally form a single whole - hypothalamic-pituitary endocrine system(Fig. 1).

Hypothalamic cells have a dual function. Firstly, they perform the same functions as any other, and secondly, they have the ability to secrete and excrete biologically active substances -neurohormones(this process is called neurosecretion). The hypothalamus and the anterior pituitary gland are connected by a common vascular system, which has a double capillary network. The first is located in the area of ​​the median eminence of the hypothalamus, and the second is in the anterior lobe of the pituitary gland. It is called the pituitary portal system.

Neuroendocrine systems of the hypothalamus:

• Hypothalamic-extrahypothalamic system
• Hypothalamic-adenopituitary system
• Hypothalamic-midpituitary system
• Gynothalamic-neurohypophyseal system

Neurosecretory cells of the hypothalamus synthesize neuropeptides that enter the anterior and posterior lobes of the pituitary gland. Neuropeptides that affect the cells of the anterior pituitary gland are called releasing factors, and the posterior one - by neurohormones (vasopressin and oxytocin).

Rice. 1. Anatomical relationship between the hypothalamus and the pituitary stalk

Dotted shading—median eminence and posterior lobe of the pituitary gland (neurohypophysis); have a neutral origin and are actually part of the hypothalamus; oblique shading - epithelial part of the pituitary gland (adenohypophysis); develops from the ectoderm of the oral bay. The role of the hypothalamic-pituitary system for the endocrine regulation of body functions is so great that it is sometimes called the “president of the endocrine society.”

From a functional point of view, releasing factors are divided into liberins(releasing factors that enhance the synthesis and secretion of the corresponding hormone in the endocrine cells of the anterior pituitary gland) and statins(releasing factors that suppress the synthesis and secretion of hormones in target cells). Hypothalamic liberins include somatostatin, gonadoliberin, thyrotropin-releasing hormone and corticoliberin, and statins are represented by somatostatin and prolactinostatin (Fig. 2).

Under the influence of a nerve impulse, these products are released into the first capillary network of the portal system and act on the glandular cells of the anterior pituitary gland through the second capillary network. Thus, information from the hypothalamus is transmitted to the pituitary gland through the humoral route. The hypothalamic-pituitary system is a typical example of the close interaction between the nervous and humoral methods of regulating functions, because a neurosecretory cell is capable of exerting a regulatory influence, not only sending ordinary nerve impulses to other neurons, but also releasing neurohormones.

All endocrine glands function on the principle of plus or minus interaction or on the principle of direct (positive) and feedback (negative) communication. The physiological essence of this interaction is to ensure the possibility of self-regulation and normalization hormonal balance body. Let's look at this in Fig. 3.

Rice. 2. Regulation of the activity of the endocrine glands by the central nervous system with the participation of the hypothalamus and pituitary gland:

TL—thyrotropin-releasing hormone; SP - somatoliberin; SS - somatostatin; PL—prolactoliberin; PS—prolactostatin; GL - gonadoliberin; CL—corticoliberin; TSH - thyroid-stimulating hormone: STH - somatotropic hormone (growth hormone): Pr - prolactin; FSH - follicle-stimulating hormone: LH - luteinizing hormone; ACTH is adrenocorticotropic hormone. Solid arrows indicate activating influence, dotted arrows indicate inhibitory influence.

Rice. 3. Scheme of regulation of the functions of the endocrine glands: > direct connection > feedback

Neurosecrets of the hypothalamus, acting on pituitary cells, regulate the release of gonadotropic hormones (direct connection). If FSH, LH and LTG are released in excess quantities, then an increase in the concentration of the hormone in the blood inhibits the neurosecretory function of hypothalamic cells (feedback). In turn, gonadotropins regulate the release of sex hormones by the gonads (direct connection). With a high titer of sex hormones (feedback), the secretion of gonadotropins is inhibited.

Rice. Hypothalamic-pituitary system

Rice. Direct and feedback connections of the hypothalamic-pituitary-peripheral glands system

So is the endocrine one.

The hypothalamic-pituitary system consists of the pituitary stalk, starting in the ventromedial region of the hypothalamus, and three lobes of the pituitary gland: adenohypophysis (anterior lobe), neurohypophysis (posterior lobe) and intercalary pituitary gland. The work of all three lobes is controlled by the hypothalamus with the help of special neurosecretory cells. These cells secrete special hormones - releasing hormones, as well as the “posterior lobe” hormones - oxytocin and vasopressin.

Structure

Hormones of the hypothalamic-pituitary system

Under the influence of one or another type of action of the hypothalamus, the lobes of the pituitary gland are distinguished various hormones, controlling the functioning of almost the entire human endocrine system. The exception is the pancreas and adrenal medulla. They have their own regulatory system.

Hormones of the anterior pituitary gland

Somatotropin

It has an anabolic effect, therefore, like any anabolic steroid, ST enhances synthesis processes (especially protein synthesis). Therefore, somatotropin is often called “growth hormone”.

When the secretion of somatotropin is impaired, three types of pathologies occur.

• When the concentration of somatotropin decreases, a person develops normally, but his height does not exceed 120 cm - “pituitary dwarfism”. Such people (hormonal dwarfs) are capable of childbearing and their hormonal background not very disturbed.
• With an increase in the concentration of somatotropin, a person also develops normally, but his height exceeds 195 cm. This pathology is called “gigantism.” During puberty (the period of activation of the reproductive system, starting at approximately 11-13 years. In young men, puberty occurs two years later than in girls, whose hormonal surge, unlike boys, is smooth and its decline is quite rapid.) increases greatly muscle mass, therefore the number of capillaries increases. The heart is not capable of this rapid growth. Because of this discrepancy, pathologies arise.
• After 20 years, the production of somatotropin decreases, therefore, the formation of cartilage tissue (as one of the aspects of growth) slows down and decreases. Therefore, the bone tissue slowly “eats” the cartilage tissue, therefore the bones have nowhere to grow except in diameter. If the production of somatotropin does not stop after 20, then the bones begin to grow in diameter. Due to this thickening of the bones, for example, the fingers become thicker, and because of this thickening, they almost lose mobility. At the same time, somatotropin also stimulates the production connective tissue, as a result of which the lips, nose, ears, tongue, etc. enlarge. This pathology is called “acromegaly”.

Thyrotropin

The target of thyrotropin is the thyroid gland. It regulates the growth of the thyroid gland and the production of its main hormone - thyroxine. An example of the action of a releasing factor: Thyroxine is necessary to increase the efficiency of oxygen respiration, thyroxine requires thyrotropin, and thyrotropin requires thyrotropin-releasing hormone, which is the releasing factor of thyrotropin.

Gonadotropins

The name gonadotropins (GT) refers to two different hormones—follicle-stimulating hormone and luteinizing hormone. They regulate the activity of the sex glands - gonads. Like other tropic hormones, gonadotropins primarily affect the endocrine cells of the gonads, regulating the production of sex hormones. In addition, they influence gamete maturation, the menstrual cycle and related physiological processes.

Corticotropic hormones

The target of CT is the adrenal cortex. It should be noted that the parathyroid gland regulates mineral metabolism (with the help of parathyroid hormone), like the adrenal cortex, so you can put regulation only on the adrenal cortex, and the pair thyroid gland will automatically work in accordance with the adrenal cortex.