Functional state of the hypothalamic-pituitary-adrenal system

The hypothalamus, the anterior pituitary and the adrenal cortex are functionally combined into the hypothalamic-pituitary-adrenal system.

The adrenal gland consists of the cortex and the brain, performing various functions. Histologically, in the adrenal cortex of an adult human, three layers are distinguished. The peripheral zone is called the glomerular zone, behind it is the fascicle( the widest middle zone of the adrenal cortex) and the mesh. The glomerular zone secrets only aldosterone. Two other layers - the bundle and reticular zones - form a functional complex secreting the bulk of adrenal cortex hormones( HA and an-drogens).

In the beacon zone of the coronid cysts, pregnenolone synthesized from cholesterol is converted to 17a-oxypregnenolone, which serves as a precursor of cortisol, androgens and estrogens. During the synthesis, 17a-hydroxyprogesterone is formed from 17a-hydroxypregnonolone, which is subsequently hydrolysed into cortisol.

To the secretion products of the beam and reticular zones are steroids that have androgenic activity: dehydroepiandrosterone( DHEA), dehydroepiandrosterone sulfate( DHEAS), androstenedione( and its 11b-analog), and testosterone. All of them are formed from 17a-oxypregnenolone.

Adrenal gland and androgen production is regulated by the hypothalamic-pituitary system. In the hypothalamus, KRG is produced through portal vessels into the anterior pituitary gland, where it stimulates

production of ACTH.ACTH causes rapid and abrupt changes in the cortical layer of the adrenal glands. In the adrenal cortex, ACTH increases the rate of cleavage of the side chain from the XC reaction, which limits the rate of steroidogenesis in the adrenal glands. These hormones( KRG-ACTH-free cortisol) are linked together by a classical loop of negative feedback - an increase in the concentration of free cortisol in the blood inhibits the secretion of CRH, and vice versa, its decrease stimulates the release of CRH by the hypothalamus.

Adrenal cortex diseases can occur either with hyperfunction( hypercorticosis), or with hypofunction( hypocorticism).Pathology, which determines the increase in the secretion of certain hormones and the reduction of others, refers to the group of dysfunctions of the adrenal cortex.

In cases of adrenal cortex diseases, the following syndromes are distinguished.

■ Hypercortisy:

□ Itenko-Cushing's disease( hypothalamic-pituitary disease);

□ Itenko-Cushing syndrome - corticosteroid( benign or malignant) or bilateral small-knee dysplasia of the adrenal cortex;

□ ACTH-ectopic syndrome: tumors of bronchi, pancreas, thymus, liver, ovaries secreting ACTH or KRG;

□ feminization and virilization syndrome( excess estrogen and / or androgens).

■ Hypocorticism:

□ Primary;

□ secondary;

□ tertiary.

■ Dysfunction of the adrenal cortex:

□ adrenogenital syndrome( ACS).

To determine the functional state of the hypothalamic-pituitary-adrenal system, the concentration of ACTH and cortisol in the blood, free cortisol in the urine, DHEAS in the blood, 17-hydroxycorticosteroids( 17-ACS) and 17-ketosteroids( 17-CS) in the urine,17a-hydroxyprogesterone( 17-GPG) in the blood.