Akademik

Abbreviation for adrenocorticotropic hormone.

- big A. a form of A., produced by certain tumors, which is a larger and more acidic peptide molecule than little A., but is not immunochemically distinguishable from it and does not exert any of the biologic effects characteristic of A.; proteolytic digestion of big A. yields hormonally active little A CTH.

- little A. a term coined to denote the conventional A. molecule when contrasted with big A..

* * *

ACTH .ā-.sē-(.)tē-'āch n a protein hormone of the anterior lobe of the pituitary gland that stimulates the adrenal cortex called also adrenocorticotropic hormone

a hormone synthesized and stored in the anterior pituitary gland, large amounts of which are released in response to any form of stress. Its release is stimulated by corticotrophin-releasing hormone. ACTH controls the secretion of corticosteroid hormones from the adrenal gland. An analogue of ACTH, tetracosactide, is administered by injection to test adrenal function (see short Synacthen test).