Functional state of the hypothalamic-pituitary system

There is a close relationship between the nervous and endocrine systems. The unity of the nervous and humoral regulation in the body is ensured by the close anatomical and functional connection of the pituitary and hypothalamus. Hypothalamus is the highest vegetative center, coordinating the functions of various systems to meet the needs of the whole organism. It plays a leading role in maintaining the optimal level of metabolism (protein, carbohydrate, fat, water and mineral) and energy, in the regulation of the body's heat balance, digestive, cardiovascular, excretory, respiratory and endocrine systems. Under the control of the hypothalamus there are such endocrine glands as the pituitary gland, the thyroid gland, the sex glands, the adrenal glands, the pancreas. The hypothalamus has extensive anatomical and functional connections with other structures of the brain.

Regulation of secretion of tropic hormones of the pituitary gland is carried out by the release of hypothalamic neurohormones. The hypothalamus forms specific mediators - the releasing hormones that enter the pituitary gland through the vessels of the portal system of the hypothalamus-pituitary gland and, acting directly on its cells, stimulate or inhibit the secretion of hormones. The network of blood capillaries belonging to the portal system of the hypothalamus-pituitary gland forms veins that pass along the pituitary foot, and then separate into the secondary capillary network in the anterior pituitary gland. Hormones of the hypothalamus and pituitary gland belong to protein and peptide hormones.

Hormones of the hypothalamus

The following hormones of the hypothalamus stimulate the secretion of adenohypophilic tropins:

• corticotropin-releasing hormone (CRH);
• thyrotropin-releasing hormone (TRH);
• gonadotropin-releasing hormone (GnRH);
• prolactin-releasing hormone (PWG);
• somatotropin-releasing hormone (STRG);
• melanotropin-releasing hormone. The blockers of pituitary hormone secretion include:
• somatostatin;
• gonadotropin-rilysin-inhibiting hormone (GRIG);
• prolactin-releasinginhibiting hormone (PRIG);
• melanostatin.

The biosynthesis of the above-mentioned neurohormones is realized not only in the hypothalamus, for example, somatostatin form D-cells of pancreatic and intestinal mucosa, as well as cerebral neurosecretory cells. TGH is formed, in addition to the hypothalamus, in other parts of the central nervous system. In addition to these hormones, ADH, oxytocin and neurofizin are still synthesized in the hypothalamus, which migrate along the nerve pathways of the pituitary foot and enter the tissue depots of the posterior lobe of the pituitary gland. Hypothalamus regulates the release of these peptides into the bloodstream.

Pituitary Hormones

The pituitary gland secretes hormones with a wide spectrum of action.

• The anterior pituitary gland synthesizes:
  • ACTH;
  • STH, or growth hormone;
  • TTG;
  • FSH;
  • LH;
  • prolactin;
  • β-lipotropic hormone;
  • propiomelanocortin.
• In the cells of the middle part of the pituitary (intermediate segment), the following syntheses are synthesized:
  • melanocyte-stimulating hormone (α-MSH);
  • corticotropin-binding medium-average peptide;
  • β-endorphin.
• In the posterior lobe of the pituitary gland are secreted:
  • ADH (arginine-vasopressin);
  • oxytocin;
  • neurofizin (precise functions are not established, promotes transport and transition to reserve forms in the posterior lobe of the pituitary gland ADH and oxytocin.

Pituitary hormones can form in other tissues of the body, mainly in malignant and benign tumors. Tumors of various organs are able to secrete ACTH, ADH, prolactin, TTG, STG, etc.

Regulation of the secretion of hormones of the hypothalamus and pituitary gland

Regulation of secretion of pituitary hormones is carried out by the nervous system, and also by the principle of feedback. For the secretion of ACTH, LH, FSH, TSH, only stimulants are known, inhibition of their secretion is effected by the hormones of the target glands (corticosteroids, sex steroids, T ₄ ). The secretion of tropic hormone is usually inhibited by an increase in the concentration of the hormone of the target gland in the blood. This negative feedback can either directly inhibit the secretion of the hormone of the hypothalamus, or alter its effect on the pituitary cells. Accumulation of secretion of the hormone adenohypophysis can inhibit the secretion of the releasing hormone of the hypothalamus.

Violation of the secretion of hormones of the hypothalamus and pituitary gland

At the basis of the violations of synthesis and secretion of hormones of the hypothalamus and pituitary gland lies the effect of the following pathogenetic mechanisms.

• Violation of the ratio of neurotransmitters in the central nervous system.
• Local disturbances in the synthesis of hormones, changes in their properties and the response of cells to the action of hormones in the hypothalamus and pituitary.
• Pathological changes in hormone receptors of pituitary cells.
• Disorders of peripheral glands functions of internal secretion and their receptors.
• Pathological resistance (non-reactivity) of target cells to the action of hormones.

The main cause of hypothalamic-pituitary diseases - a violation of the relationship of the central nervous system, hypothalamus, pituitary gland and peripheral glands of internal secretion. In order to choose effective methods of treatment, it is necessary to establish at what level a disruption of the relationship in the system of hormonal regulation has occurred.

[1], [2], [3], [4], [5], [6], [7], [8],