Hypothalamic pituitary system endocrinology. Hypothalamic-pituitary system

Pituitary- endocrine gland located in the pituitary fossa of the sella turcica of the sphenoid bone (Fig. 1). The mass of the pituitary gland is 0.5-0.7 g, dimensions 1.3x0.6x1.0 cm, but they can vary depending on age and gender (in women it is larger than in men). The pituitary gland has two lobes: the anterior (adenohypophysis) and the posterior (neurohypophysis). The adenohypophysis consists of three types of cells: acidophilic, basophilic, which make up the group of chromophiles, and chromophobes. Acidophilic (eosinophilic) cells produce growth hormone (GH; somatotrophs) and prolactin (lactotrophs), basophilic cells produce thyroid-stimulating hormone (TSH; thyrotrophs), adrenocorticotropic hormone (ACTH, corticotrophs), as well as gonadotropins (gonadotrophs): follicle-stimulating hormone (FSH) and luteinizing (LH) hormones. Chromophobic cells are considered as the source from which chromophiles differentiate.

Rice. 1. Pituitary gland (top view)

The neurohypophysis terminates the fibers of the hypothalamic-pituitary tract, coming from the supraoptic and paraventricular nuclei of the hypothalamus. The axons of neurosecretory cells end in axovasal synapses, through which vasopressin (antidiuretic hormone) and oxytocin secreted in the nuclei of the hypothalamus enter.

The adenohypophysis is a key regulator endocrine system. The hormones it secretes (LH, FSH, TSH, ACTH) regulate the function of peripheral endocrine glands: thyroid, adrenal cortex, gonads. Other hormones (GH, prolactin) have a direct effect on target organs and tissues.

Hypothalamus located at the base of the brain and bounded in front by the optic chiasm, behind by the mamillary bodies, and on the sides by the optic nerves. It is introduced into the hypothalamic region from above III ventricle brain The mass of the hypothalamus in an adult is about 4 g. The pathways closely connect the hypothalamus with neighboring structures of the brain. The relationship between the pituitary gland and hypothalamus is carried out through the portal system. Pituitary portal system includes primary capillary network, which contacts the terminal axons of the arcuate, ventromedial and paraventricular nuclei of the hypothalamus. The capillaries of the primary plexus are collected into portal veins, running along the pituitary stalk into the anterior lobe of the pituitary gland, where they break up into the secondary capillary network. The sinusoids of the secondary capillary network collect in the efferent veins, through which blood enriched with hormones of the anterior pituitary gland enters the systemic blood flow. The currently known hormones of the hypothalamus are divided into hormones that enhance (releasing hormones, liberins) and inhibit (statins) the release of the corresponding tropic hormones, while their role is not limited to the scheme one Liberia (statin) - one pituitary hormone. Thus, thyroliberin can stimulate the production of TSH and prolactin; GnRH is a common releasing hormone for LH and FSH; somatostatin suppresses the secretion of GH and ACTH.

Prolactin- a protein hormone whose main physiological function is to ensure lactation. The process of breastfeeding has a stimulating effect on the secretion of prolactin. The main inhibitor of prolactin secretion is dopamine, synthesized in the hypothalamus.

Growth hormone(GH, somatotropin) is a polypeptide hormone whose effects on organs and tissues are realized by insulin-like growth factor-1 (IGF-1), synthesized in the liver under the influence of GH. The main effect of GH in children and adolescents is the stimulation of longitudinal bone growth (mainly long tubular and to a lesser extent spongy). In addition, GH stimulates protein synthesis and nitrogen retention, and has lipolytic and antinatriuretic effects. The introduction of physiological doses of GH produces a short-term insulin-like (lowering glycemia) and then a counter-insular effect. The synthesis and secretion of GH is controlled by two hypothalamic neuropeptides - GH releasing hormone (somatoliberin, GR-RH) and somatostatin. During the day, plasma GH levels remain low; GH peaks after a meal and increases progressively during sleep. In growing children, the integral daily production of GH is significantly higher than in adults.

Luteinizing hormone(LH) in the ovaries stimulates ovulation and androgen synthesis by theca cells, and in the testes it regulates testosterone production by Leydig cells.

Follicle-stimulating hormones(FSH) in the ovaries stimulates the growth of granulosa cells and the secretion of estrogens; in the testicles - together with testosterone, stimulates spermatogenesis.

Adrenocorticotropic hormone(ACTH, corticotropin) is a stimulator of the production of cortisol and androgens in the adrenal cortex.

Main function thyroid-stimulating hormone(TSH) is the stimulation of the synthesis and secretion of hormones thyroid gland, as well as the trophic effect of nathyroid cells.

Independent and largely autonomous system is neurohypophysis, consisting, as indicated, of the axons of the supraoptic and paraventricular nuclei of the hypothalamus.

Vasopressin(arginine vasopressin, antidiuretic hormone, ADH) is a protein consisting of 9 amino acids. ADH receptors are located in the distal convoluted tubules of the nephron; their activation leads to increased water reabsorption. IN physiological conditions ADH secretion is regulated by osmoreceptors of the hypothalamus: plasma hyperosmolarity leads to stimulation ADH secretion. Other indirect stimulators of ADH secretion are hypovolemia and arterial hypotension.

Oxytocin just like vasopressin, it consists of 9 amino acids, but differs from it in two amino acid residues. Oxytocin, acting on the muscles of the uterus, increases the strength of its contractions, thus ensuring labor and postpartum contractions of the uterus. By stimulating the contraction of myoepithelial cells in the alveoli of the mammary glands, oxytocin promotes the flow of milk into the milk ducts. Physiological stimulators of oxytocin secretion are stretching of the woman's genital tract and breastfeeding.

Dedov I.I., Melnichenko G.A., Fadeev V.F.

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

The main functional significance of the hypothalamus is pituitary system- regulation of the body’s vegetative functions. 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 various parts- hypothalamus (see) and 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.

Due to the large accumulation of axon endings 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).

Only in the case of the presence of individual adenomas can local damage to the adenohypophysis be determined. Lesions of the hypothalamic-pituitary system caused by infectious processes, neoplasms, or trauma to the skull and brain, leading to a local effect on the centers of the hypothalamus or disruption of the integrity of the hypothalamic-pituitary connections, usually lead to deep and persistent disorders of various aspects of metabolism (water-salt, fat, carbohydrate), disruption of thermoregulation , function of the genital organs and decreased body resistance (see Hypothalamic syndrome). The most characteristic and studied are the following diseases: diabetes insipidus (see), pituitary cachexia (see) and Itsenko-Cushing disease (see). Sometimes, when the gray tubercle is affected, diabetes mellitus also develops (see).

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.

Basically, regulation within the endocrine system is carried out through hormonal and neurohormonal mechanisms. The highest center of neurohormonal control, which switches regulation from the nervous system to the endocrine system, is hypothalamic-pituitary system . It includes the hypothalamus, one of the parts of the diencephalon, and the pituitary gland, an endocrine gland that is localized in the brain.

In the hypothalamic-pituitary structural-functional association, two relatively independent systems. The first system consists of the supraoptic and paraventricular nuclei of the hypothalamus, which are connected to the pituitary gland hypothalamic-pituitary nerve tract.

The second system consists of the hypophysiotropic zone of the hypothalamus, which is connected to the pituitary gland venous vascular network. In the hypophysiotropic zone of the hypothalamus, neurohormones are synthesized, which are called releasing factors .

Neurohormone- these are specific biologically active substances that are produced by nerve cells and have a regulatory effect on the functions of target cells far from the place of their formation.

Through the portal venous vascular network, neurohormones enter the pituitary gland, where they have a regulatory effect on its hormone-forming function.

There are two groups of releasing factors: liberins And statins.

Liberians stimulate the synthesis and secretion of pituitary hormones. These include:

1) corticoliberin,

2) thyroliberin,

3) gonadoliberins - luliberin (releasing factor of luteinizing hormone) and foliberin (releasing factor of follicle-stimulating hormone),

4) somatoliberin,

5) prolactoliberin,

6) melanoliberin.

Statins inhibit the formation and release of pituitary hormones. These include:

1) somatostatin,

2) melanostatin,

3) prolactostatin.

Neurohormonal regulation of the hormone-forming function is carried out automatically according to the cybernetic feedback principle. With an excess of the effector hormone in the blood, the synthesis and release of liberins is inhibited, and statins are activated. In the case of a lack of effector hormone, on the contrary, the incretion of activators increases, and the incretion of inhibitors decreases.

Anatomically, the pituitary gland is divided into anterior, middle (intermediate) and posterior lobes. The intermediate lobe of the pituitary gland in humans is poorly expressed. Together with the anterior lobe, they are functionally united into the adenohypophysis.

In the anterior lobe of the pituitary gland, two groups of hormones of protein-peptide nature are synthesized - tropic and effector.

Tropic hormones anterior lobe of the pituitary gland - thyrotropic (thyrotropin), adrenocorticotropic (corticotropin) and gonadotropic (gonadotropins), regulate secretory function other endocrine glands.

Thyrotropic hormone(TSH) stimulates the activity of the thyroid gland. Adrenocorticotropic hormone (ACTH) stimulates the activity of the adrenal cortex.

TO gonadotropins , which provide reproductive processes, include luteinizing And follicle-stimulating hormones.

Luteinizing hormone(LH) is key for the production of male and female sex hormones.

In women it also stimulates ovulation– release of female germ cells (eggs) from the ovary. Follicle stimulating hormone (FSH) in men stimulates the proliferation of spermatogenic epithelium and activates spermatogenesis. In women, FSH stimulates the growth and development of ovarian follicles.

The physiological effects of gonadotropins are associated with their stimulating effect on the gonads. Therefore, when the adenohypophysis is damaged, atrophy of the gonads is observed.

Effector hormones anterior pituitary gland - somatotropic (somatotropin, growth hormone), prolactin And lipotropins, directly affect executive bodies (effector organs) and target cells.

Somatotropic hormone(STG):

1) stimulates the development of soft tissues of the body, as well as linear growth tubular bones,

2) has a direct anabolic effect on protein metabolism(stimulates the transport of amino acids into cells, as well as the biosynthesis of protein from amino acids),

3) in physiological concentrations increases the level of glucose in the blood,

4) stimulates lipolysis (fat breakdown) and mobilization of fat from the depot.

Excessive formation and secretion of growth hormone in children leads to the development of gigantism, which manifests itself in a proportional increase in body size. In adults, excess growth hormone leads to acromegaly - uneven growth of skeletal bones, as well as splanchomegaly - growth of internal organs.

Insufficient internal secretion of growth hormone in children causes pituitary dwarfism (dwarfism), which manifests itself in delayed physical and sexual development.

Main physiological effect prolactin in men - stimulation of the activity of the prostate and testes. In women, it stimulates the production of milk by the mammary glands during lactation,

The main physiological effect lipotropins is a direct fat-mobilizing and lipolytic effect.

The intermediate lobe of the pituitary gland produces the effector melanocyte-stimulating hormone (MSH, melanotropin). The main physiological effect of MSH is the activation of pigment metabolism in cells.

In humans, melanotropin is produced in small quantities and, therefore, does not play a significant role in pigment metabolism. Its importance increases in animals covered with fur, as well as in creatures that can change the color of their body (chameleon, octopus, some types of fish).

The cells of the posterior lobe of the pituitary gland (neurohypophysis) do not synthesize hormones. They function as a depot of oxytocin and vasopressin, which are produced by neurons of the supraoptic and paraventricular nuclei of the hypothalamus.

oxytocin :

1) stimulates contraction of the smooth muscles of the uterus,

2) stimulates the contraction of myoepithelial cells mammary glands, increasing milk production during breastfeeding.

The flow of oxytocin into the blood increases during pregnancy, especially before childbirth, and during lactation.

Main physiological effects vasopressin (antidiuretic hormone, ADH):

1) in high concentrations increases blood pressure due to contraction of the smooth muscles of arterioles,

2) reduces urine output (diuresis) by reducing water reabsorption in the kidneys.

The synthesis of ADH in the hypothalamus and its release from the posterior lobe of the pituitary gland increases:

1) with hypovolemia - a decrease in the volume of circulating blood,

2) with hyperosmia - an increase in the osmotic pressure of blood plasma,

3) when experiencing pain, increased psycho-emotional tension and stress.

Home Endocrinology Hypothalamic-pituitary system

Hypothalamic-pituitary system

The pituitary gland (lower cerebral appendage) can no longer be considered a “master gland.” Information from almost all parts of the central nervous system first enters the hypothalamus and only from there is transmitted to the pituitary gland.

The hypothalamus influences the activity of the anterior and posterior pituitary glands in two ways. Neurohormones synthesized in the hypothalamus enter through special system portal vessels directly into the anterior lobe of the pituitary gland (adenohypophysis), where they regulate the synthesis and secretion of the six main peptide hormones of the anterior lobe; Pituitary hormones, in turn, regulate the activity of the peripheral endocrine glands (thyroid, adrenal glands and gonads), as well as body growth and lactation. There are no direct nerve connections between the hypothalamus and the anterior pituitary gland. In contrast, the posterior lobe of the pituitary gland (neurohypophysis) concentrates axons originating in the bodies of nerve cells located in the hypothalamus. These axons serve as a storage site for two peptide hormones synthesized in the hypothalamus and regulating water balance, milk secretion and uterine contraction in the periphery. In some animal species there is also an intermediate lobe, located between the anterior and posterior lobes of the pituitary gland. It can also be found in human fetuses, but is most often absent in adults.

Almost all hormones produced in the hypothalamus or pituitary gland are secreted in waves: short periods of activity and rest quickly follow each other. In addition, the secretion of a number of hormones (for example, adrenocorticotropic hormone (ACTH), growth hormone (GH), prolactin (PRL)) also has a circadian, or daily, rhythmicity, increasing at certain times of the day; secretion of other hormones (for example, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) during menstrual cycle) has more frequent, ultradian rhythms.

Hypothalamic regulation of the anterior pituitary gland

Reaching the anterior lobe of the pituitary gland through the portal vessels, various releasing and inhibitory hormones secreted by the hypothalamus bind to specific cell membrane receptors and trigger the chain biochemical reactions, stimulating or inhibiting the secretion of pituitary hormones into the general bloodstream. To date, six hypothalamic neurohormones have been identified. With the exception of one of the biogenic amines, dopamine, they are all small peptides. Some of them are produced not only in the hypothalamus, but also in the periphery, participating in the work of the local paracrine regulation system, mainly in gastrointestinal tract. These neurohormones are capable of regulating the secretion of not one, but several pituitary hormones, but their effects are highly specific. Regulation of the secretion of most hormones of the anterior pituitary gland is carried out by stimulating signals coming from the hypothalamus; BPD alone is primarily under inhibitory control (see below).

Thyrotropin-releasing hormone (TRH)(thyrotropin-releasing hormone) stimulates the synthesis and secretion of both thyroid-stimulating hormone (TSH) (thyrotropin) and PRL. However, whether TRH stimulates PRL secretion under physiological conditions is unclear. At pathological conditions TRH is capable of stimulating the synthesis and secretion of GH.

Gonadotropin releasing hormone (GnRH), also called luteinizing hormone releasing hormone (LHRH)(trivial name - gonadoliberin), under physiological conditions and with a single administration, stimulates the secretion of both LH and FSH. However, with continuous administration of exogenous GnRH, the secretion of LH and FSH, while initially increasing, is soon inhibited due to the “down regulation” of pituitary GnRH receptors by this hormone itself. This observation served as an impetus for the development of long-acting GnRH agonists, which have a large clinical significance in situations requiring “castration by medical indications" GnRH analogues have been successfully used to suppress the secretion of androgens in prostate cancer, ovarian steroids in women with endometriosis and uterine leiomas, and sex steroids in true precocious puberty (see also precocious puberty). In some situations, a pulse of GnRH to the pituitary gland stimulates the secretion of PRL.

Somatostatin has an inhibitory regulatory effect on the synthesis and secretion of GH and TSH. GH secretion is stimulated growth hormone releasing hormone(GR-RH, or somatoliberin) and is inhibited by somatostatin, and the rate of GH production depends on the relationship between these two effects. In the pancreas, somatostatin also inhibits insulin secretion.

Corticotropin releasing hormone (CRH)(corticoliberin) stimulates the secretion of ACTH by the pituitary gland (see below).

Dopamine is the main regulator of PRL levels, inhibiting its synthesis and secretion. When the pituitary stalk (which connects the pituitary gland to the hypothalamus) is cut, the secretion of PRL increases, while the secretion of all other hormones of the anterior pituitary gland decreases. In some situations, dopamine also inhibits the secretion of LH, FSH and TSH.

Many diseases of the hypothalamus (in particular, tumors, encephalitis and other inflammatory processes) can alter the secretion of hypothalamic neurohormones and thereby affect the function of the pituitary gland. The resulting clinical syndromes manifested by changes in the secretion of pituitary hormones.

Hypothalamic-pituitary system and its functions

Different neurohormones are synthesized in different centers of the hypothalamus, so the secretion of only one or several neuropeptides is often impaired. In Kallman syndrome, for example, hypogonadism is associated with a deficiency of hypothalamic GnRH (see hypothalamic-pituitary disorders). However, damage to the hypothalamus may be accompanied by a decrease in the secretion of all hypothalamic neurohormones, causing secondary panhypopituitarism with hyperprolactinemia and galactorrhea (due to decreased secretion of dopamine). Pathology of the hypothalamus can also lead to hypersecretion of neurohormones, being in some cases the cause of premature puberty and Cushing's syndrome.

Ed. N. Alipov

“Hypothalamic-pituitary system” - article from the Endocrinology section

Regulation of adrenal cortex function.

Morphological and functional adrenal integrity controlled by adrenocorticotropic hormone (ACTH) of the pituitary gland and hypothalamus. The hypothalamus, pituitary gland and adrenal cortex are a single system that plays an extremely important role in maintaining homeostasis and the body's resistance to damage caused by environmental stressors. However, other endocrine organs and mechanisms also take part in these processes of maintaining the constancy of the internal environment of the body.

Pituitary influences on adrenal function limited by the regulation of glucocorticoid secretion. Pituitary insufficiency causes a decrease in the size of the zona fasciculata of the adrenal glands, in which glucocorticoids are synthesized. The zona glomerulosa, which produces aldosterone, does not change after hypophysectomy and, therefore, the secretion of aldosterone is not regulated by the hypothalamic-hyophyseal system.

According to most Based on the theory, aldosterone secretion is primarily regulated by the kidneys through the release of a special enzyme, renin, by the juxtaglomerular apparatus in response to changes in glomerular blood flow, blood volume, and other influences. Renin released into the blood causes the formation of a substance with high biological activity, angiotensin, which stimulates the production of aldosterone by the adrenal glands.
Other hypothesis attributes the regulating effect on aldosterone secretion to a special substance (glomerulotropin) secreted by the pineal gland or its surrounding tissue.

Normal secretion glucocorticoids controlled by a negative feedback mechanism between the adrenal cortex and ACTH of the adenohypophysis. Plasma corticoid levels regulate the secretion of ACTH, which in turn regulates the production of cortisol. This interaction does not occur directly between the pituitary gland and the adrenal glands, but is mediated through the hypothalamus, which responds to plasma cortisol and in turn regulates the production of ACTH by the pituitary gland.
However, hypothalamic regulation of function pituitary gland is not completely autonomous. It is modulated by neighboring structures, especially the limbic system.

In the absence of stress, secretion ACTH increases when you fall and slows down when the level of cortisol in the blood rises. When under stress, for example during surgical interventions, regulation of secretion. ACTH changes so that increased plasma cortisol no longer suppresses ACTH secretion as it normally does.
The result of this is an increase in content ACTH in the plasma, which stimulates the secretion of cortisol, which leads to an increase in the content of corticosteroids in the plasma and an increase in their excretion in the urine.

Hypothalamic-pituitary-adrenal system

Hypothalamic-pituitary-adrenal system is a neuroendocrine mechanism through which emotional, neurogenic and other types of stress, affecting the nervous system, cause a reaction of the pituitary-adrenal system. This reaction is caused by numerous changes in the external environment, which lead to an increase in the biosynthesis and secretion of adrenal hormones. The afferent impulses caused by these changes stimulate the release of ACTH into the blood in quantities large enough to satisfy the body's increased need for adrenal hormones.

Selye regarded this reaction as one of the links in the “general adaptation syndrome”, in which the pituitary-adrenal system acts as a mechanism that ensures the maintenance of homeostasis under stress conditions. Investigating this problem, Selye described relatively common features for various forms of stress and formulated the position that depletion or prolonged hyperfunction of the pituitary gland-adrenal cortex system plays a significant role in the pathogenesis of diseases such as hypertension, arthritis, peptic ulcer, diabetes, etc.

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etc., which he called diseases of adaptation.

Although pituitary-adrenal reaction to external influences and is a very important mechanism in maintaining the integrity of the body, however, other endocrine and nervous mechanisms are also involved in this process, which in some cases explain the pathogenesis of the above-mentioned diseases better than a violation of the adaptive properties of the pituitary-adrenal system.

With long-term administration large doses glucocorticoids hypoplasia of the zona fasciculata occurs, as can be predicted. Complete atrophy this tissue does not occur and retains the ability to respond to corticotropin stimulation. The pituitary gland (or perhaps the hypothalamus) no longer responds to decreased cortisol levels in the blood. Thus, when appropriate therapy is stopped, the body becomes unable to adequately respond to stress and, if exposed to stress factors, may develop acute failure adrenal glands

Porter-Silber color reaction. Identification of 17-ketosteroids, ketogenic steroids
Isotope methods for diagnosing corticosteroids. Daily secretion of corticosteroids
Binding, exchange of cortisol and cortisone in the blood
Physiology of the adrenal cortex: electrolyte and water metabolism
The role of the adrenal cortex in the regulation of protein, carbohydrate, and fat metabolism
The influence of the adrenal cortex on blood and immunity
Effect of the adrenal glands on the nervous system, blood circulation, skin and bones
Regulation of adrenal cortex function. Hypothalamic-pituitary-adrenal system
Pharmacological inhibition and dysfunction of the adrenal cortex
Acute adrenal insufficiency: causes and treatment

The hypothalamic-pituitary tract (Fig. 9-12) is formed by the axons of neurosecretory neurons of the hypothalamus. Hormones synthesized in neurosecretory neurons reach the axo-vasal synapses of the neurohypophysis using axonal transport.

Rice. 9-12. Hypothalamic-pituitary tract. The pituitary gland is formed by two glands, the adenohypophysis (anterior lobe) and the neurohypophysis (posterior lobe). In both cases, the control of hormone production and secretion is controlled by the hypothalamus, but the mechanisms of such control are different. Neurons with perikarya large sizes, localized in the hypothalamus, secrete releasing hormones into the lumen of the capillaries in the area of the median eminence and infundibulum. Perikarya of neurosecretory cells form clusters near the wall of the third ventricle. These are the arcuate, paraventricular and ventromedial nuclei, the middle preoptic and periventricular areas. The capillaries of the primary network collect blood into the long portal veins. Through them, hypothalamic releasing hormones enter the pituitary stalk and then into the anterior lobe. The axons of another group of small neurosecretory cells descend into the pituitary stalk over a considerable length and release releasing hormones into the capillary plexus (also the primary network), located directly in the stalk. Short portal veins carry releasing hormones to the secondary capillary network of the anterior lobe.

Hypothalamic-pituitary system. Pineal gland

Consequently, the portal veins connect the primary capillary network with the secondary one. Large neurons of the paraventricular and supraoptic nuclei of the hypothalamus synthesize vasopressin and oxytocin. Along the axons of these neurosecretory cells, these hormones enter the posterior lobe, are released from the nerve terminals and enter the lumen of numerous vessels that form a plexus here.

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Hypothalamic-pituitary system

morphofunctional combination of the structures of the hypothalamus and pituitary gland, which take part in the regulation of the basic autonomic functions of the body. Various releasing hormones produced by the hypothalamus (see Hypothalamic neurohormones) have a direct stimulating or inhibitory effect on the secretion of pituitary hormones. Moreover, between the Hypothalamus and the Pituitary gland There are also feedback connections with the help of which the secretion of their hormones is regulated. The feedback principle here is expressed in the fact that with an increase in the production of endocrine glands of their hormones, the secretion of hypothalamic hormones decreases (see Neurohumoral regulation of functions) . The release of pituitary hormones leads to changes in the function of the endocrine glands; the products of their activity enter the bloodstream and, in turn, affect its functions.

The main structural and functional components of G.-g. With. are nerve cells two types - neurosecretory, producing peptide vasopressin and, and cells, the main product of which is monoamines (monoaminergic neurons). Peptidergic cells form large nuclei - supraoptic, paraventricular and posterior. The neurosecretion produced inside these cells enters the nerve endings of the nerve processes with the current of neuroplasm. The bulk of the substances enters the posterior lobe of the pituitary gland, where the nerve endings of the axons of neurosecretory cells are in close contact with the capillaries, and passes into. In the mediabasal region of the hypothalamus there is a group of vaguely formed nuclei, the cells of which are capable of producing. The secretion of these hormones is regulated by the ratio of the concentrations of norepinephrine, acetylcholine and serotonin in the hypothalamus and reflects the functional state of the visceral organs and the internal environment of the body. According to many researchers, as part of the G.-g. With. It is advisable to distinguish the hypothalamic-adenohypophyseal and hypothalamic-neurohypophyseal systems. In the first, the synthesis of hypothalamic neurohormones (releasing hormones) is carried out, inhibiting or stimulating the secretion of many pituitary hormones, in the second - the synthesis of vasopressin (antidiuretic hormone) and oxytocin. Both of these hormones, although synthesized in the hypothalamus, accumulate in the neurohypophysis. In addition to the antidiuretic effect, vasopressin stimulates the synthesis of pituitary adrenocorticotropic hormone () and the secretion of 17-ketosteroids. affects the smooth muscles of the uterus, enhances labor, and participates in the regulation of lactation. A number of hormones of the anterior pituitary gland are called tropic. This is a hormone, ACTH, somatotropic hormone, or growth hormone, follicle-stimulating hormone, etc. Melanocyte-stimulating hormone is synthesized in the intermediate lobe of the pituitary gland. Vasopressin and oxytocin accumulate in the posterior lobe.

In the 70s It was found that in the tissues of the pituitary gland the synthesis of a number of biologically active substances peptide nature, which were later assigned to the group of regulatory peptides (Regulatory peptides) . It turned out that many of these substances, in particular endorphins, enkephalins, lipotropic hormone and even ACTH, have one common precursor - the high molecular weight protein proopiomelanocortin. The physiological effects of regulatory peptides are diverse. On the one hand, they have an independent influence on many functions of the body (for example, learning, behavioral reactions), on the other hand, they actively participate in the regulation of the activity of the g.-g. itself. pp., influencing the hypothalamus, and through many aspects of the body’s vegetative activity (relieve pain, cause or reduce feelings of hunger or thirst, affect intestinal motility, etc.). Finally, these substances have a certain effect on metabolic processes (water-salt, carbohydrate, fat). Thus, having an independent spectrum of action and closely interacting with the hypothalamus, it participates in the unification of the entire endocrine system and regulation of the processes of maintaining the constancy of the internal environment of the body at all levels of its life activity - metabolic to behavioral. The importance of the hypothalamus-pituitary gland complex for the vital functions of the body is especially evident during the differentiation of the pathological process within the framework of G.-G. With. for example, as a result of complete or partial destruction of the structures of the anterior pituitary gland, as well as the centers of the hypothalamus that secrete releasing hormones, symptoms of adenohypophysis insufficiency develop, characterized by reduced secretion of growth hormone, prolactin, and other hormones. Clinically, this can be expressed in pituitary dwarfism, hypothalamic-pituitary cachexia, neurogenic anorexia, etc. (see Hypothalamic-pituitary insufficiency) . Lack of synthesis or secretion of vasopressin may be accompanied by the occurrence of diabetes insipidus syndrome, the main cause of which is the hypothalamic-pituitary tract, the posterior lobe of the pituitary gland, or the supraoptic and paraventricular nuclei of the hypothalamus. Similar manifestations accompany hypothalamic (Hypothalamic syndromes) .

Bibliography: Aleshin B.V. Histophysiology of the hypothalamic-pituitary system, M., 1971, bibliogr.; Tonkikh A.V. Hypothalamic-pituitary region and regulation of physiological functions of the body, M., 1968; and metabolism, ed. F. Feliga et al., . from English, vol. 1, M., 1985.

1. Small medical encyclopedia. - M.: Medical encyclopedia. 1991-96 2. First medical care. - M.: Great Russian Encyclopedia. 1994 3. Encyclopedic Dictionary medical terms. - M.: Soviet Encyclopedia. - 1982-1984.

See what the “Hypothalamic-pituitary system” is in other dictionaries:

The hypothalamic-pituitary system is a combination of the structures of the pituitary gland and hypothalamus, performing the functions of both the nervous system and the endocrine system. This neuroendocrine complex is an example of how closely connected in the body... ... Wikipedia

The neuroendocrine complex of vertebrates is formed by the hypothalamus and pituitary gland. Basic value of G. g.s. regulation of the body’s vegetative functions and reproduction. Neurosecretory centers are concentrated in the hypothalamus, consisting of neurosecretory bodies... ... Biological encyclopedic dictionary

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The hypothalamic-pituitary system plays a critical 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 cartilage has already ossified and the growth of 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 formation 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 released 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).

Encyclopedic YouTube

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Introduction to the Endocrine System

Hypothalamic-pituitary system

Endocrine system 2. Hypothalamus

Subtitles

I'm at Stanford Medical School with Neil Gesundheit, one of the faculty. Hello. What do we have today? Today we’ll talk about endocrinology, the science of hormones. The word "hormone" comes from Greek word, meaning "stimulus". Hormones are chemical signals that are produced in certain organs and act on other organs, stimulating and controlling their activity. That is, they communicate between organs. Yes, that's right. These are means of communication. That's the right word. This is one of the types of communication in the body. For example, nerves go to muscles. To contract a muscle, the brain sends a signal along the nerve that goes to the muscle, and it contracts. And hormones are more like Wi-Fi. No wires. Hormones are produced and carried through the bloodstream like radio waves. This is how they affect distantly located organs without having a direct physical connection with them. Are hormones proteins or something else? What kind of substances are these anyway? Based on their chemical nature, they can be divided into two types. These are small molecules, usually derivatives of amino acids. Their molecular weight ranges from 300 to 500 daltons. And there is big squirrels containing hundreds of amino acids. It's clear. That is, these are any signaling molecules. Yes, they are all hormones. And they can be divided into three categories. There are endocrine hormones that are released into the bloodstream and work remotely. I'll give examples in just a minute. There are also paracrine hormones that have local effects. They act at a short distance from the place where they were synthesized. And the hormones of the third, rare category are autocrine hormones. They are produced by a cell and act on the same cell or a neighboring one, that is, at a very short distance. It's clear. I would like to ask. About endocrine hormones. I know that they are released somewhere in the body and bind to receptors, then they act. Paracrine hormones have a local effect. Is the action weaker? Typically, paracrine hormones enter the bloodstream, but their receptors are located very close. This arrangement of receptors determines the local nature of the action of paracrine hormones. It’s the same with autocrine hormones: their receptors are located right on this cell. I have a stupid question: there are endocrinologists, but where are the paracrinologists? Good question, but they don't exist. Paracrine regulation was discovered later and studied within the framework of endocrinology. It's clear. Endocrinology studies all hormones, not just endocrine ones. Exactly. Well said. This figure shows the main endocrine glands, about which we will talk a lot. The first is in the head, or rather at the base of the brain. This is the pituitary gland. Here he is. This is the main one endocrine gland, which controls the activity of other glands. For example, one of the hormones of the pituitary gland is thyroid-stimulating hormone, TSH. It is secreted by the pituitary gland into the bloodstream and acts on the thyroid gland, where there are many receptors for it, causing it to produce thyroid hormones: thyroxine (T4) and triiodothyronine (T3). These are the main thyroid hormones. What are they doing? They regulate metabolism, appetite, heat production, even muscle function. They have many different effects. Do they stimulate overall metabolism? Exactly. These hormones speed up metabolism. High frequency heart rate, rapid metabolism, weight loss are signs of excess of these hormones. And if there are few of them, then the picture will be completely opposite. This good example that there should be exactly as many hormones as needed. However, let's return to the pituitary gland. He is in charge and sends orders to everyone. Exactly. It has feedback to stop TSH production in time. As a device, it monitors hormone levels. When there are enough of them, it reduces TSH production. If there are few of them, it increases the production of TSH, stimulating the thyroid gland. Interesting. What else? Well, signals to the other glands. In addition to thyroid-stimulating hormone, the pituitary gland secretes adrenocorticotropic hormone, ACTH, influencing the adrenal cortex. The adrenal gland is located at the pole of the kidney. The outer layer of the adrenal gland is the cortex, stimulated by ACTH. It does not belong to the kidney; they are located separately. Yes. They are related to the kidney only by a very rich blood supply due to their proximity. Well, the kidney gave the gland its name. Well, that's obvious. Yes. But the functions of the kidney and adrenal gland are different. It's clear. What is their function? They produce hormones such as cortisol, which regulates glucose metabolism, blood pressure and well-being. As well as mineralocorticoids, such as aldosterone, which regulates water-salt balance. In addition, it secretes important androgens. These are the three main hormones of the adrenal cortex. ACTH controls the production of cortisol and androgens. We’ll talk about mineralocorticoids separately. What about the other glands? Yes, yes. The pituitary gland also secretes luteinizing hormone and follicle stimulating hormone, abbreviated LH and FSH. We need to write this down. They affect the testes in men and the ovaries in women, respectively, stimulating the production of germ cells, as well as the production of steroid hormones: testosterone in men and estradiol in women. Is there anything else? There are two more hormones from the anterior pituitary gland. It is a growth hormone that controls the growth of long bones. The pituitary gland is very important. Yes, very much. STG for short? Yes. Somatotropic hormone, also known as growth hormone. There is also prolactin, which is necessary for breastfeeding newborn baby. What about insulin? A hormone, but not from the pituitary gland, but at a lower level. Like the thyroid gland, the pancreas secretes its hormones. The gland tissue contains islets of Langerhans, which produce endocrine hormones: insulin and glucagon. Without insulin, diabetes develops. Without insulin, tissues cannot receive glucose from the bloodstream. In the absence of insulin, symptoms of diabetes occur. In the figure, the pancreas and adrenal glands are located close to each other. Why? Correctly noted. There is good venous outflow, which allows vital important hormones get into the blood faster. Interesting. I think that's enough for now. In the next video we will continue this topic. OK. And we will talk about the regulation of hormone levels and pathologies. Fine. Thank you very much. And thank you.

Structure

There are two types of releasing factors.

liberating (under their action, the cells of the adenohypophysis release hormones)
stopping (under their action the excretion of adenohypophysis hormones stops)

The hypothalamus influences the neurohypophysis and intercalary lobe with the help of special nerve fibers, and not neurosecretory cells.

Hormones of the hypothalamic-pituitary system

Under the influence of one or another type of influence of the hypothalamus, the pituitary gland secretes various hormones that control 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.) muscle mass increases greatly, therefore the number of capillaries increases. The heart is not capable of such rapid growth. Because of this discrepancy, pathologies arise. For example, vegetative-vascular dystonia (VSD), often found in adolescents.
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 is slowly “eaten away” 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. become enlarged. 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