adrenocorticotropic hormone (ACTH)

The hypothalamus sends CRH to the pituitary, which responds by secreting ACTH. ACTH then causes the adrenals to release cortisol into the bloodstream

The hypothalamus sends CRH to the pituitary, which responds by secreting ACTH. ACTH then causes the adrenal glands to release cortisol into the bloodstream

molecule of adrenocorticotropic hormone (ACTH)

Molecule of ACTH

A polypeptide hormone, consisting of 39 amino acids, which is synthesized from POMC (pre-opiomelanocortin) and secreted from corticotropes in the anterior lobe of the pituitary gland in response to the hormone corticotropin-releasing hormone (CRH) released by the hypothalamus. Adrenocorticotropic hormone (also called ACTH or corticotropin) is secreted in short bursts every few hours and is increased by stress. In turn, ACTH controls secretion of corticosteroids, including cortisol (hydrocortisone), aldosterone, and androgens, by the adrenal glands. Most important of these is its stimulation of cortisol production.

ACTH production is partly controled by the hypothalamus and partly by the level of cortisol in the blood. When ACTH levels are high, the production of cortisol is increased; this, in turn, suppresses the release of ACTH from the pituitary. If ACTH levels are low, cortisol production falls and the hypothalamus releases factors that stimulate the pituitary to increase ACTH production.

Medical uses of ACTH

ACTH has been used in an effort to induce remission in multiple sclerosis, though its efficacy in this respect is uncertain. ACTH is also used to diagnose disorders of the adrenal galnds and, rarely, to treat inflammatory disorders, such as arthritis, ulcerative colitis, and some types of hepatitis.

Disorders

A tumor of the pituitary gland can cause excessive ACTH production which, in turn, leads to overproduction of cortisol by the adrenal cortex, resulting in Cishing's syndrome. Insufficient ACTH production due, for example, to underactivity of pituitary gland (hypopituitarism), is rare. When it does occur, it causes adrenal failure.

Related category

• BIOCHEMISTRY

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