adrenocorticotroof

Adrenocorticotrophic hormone, commonly abbreviated ACTH and also known as adrenocorticotrophin, is a peptide hormone produced by the corticotroph cells of the anterior pituitary gland. It is derived from the prohormone proopiomelanocortin (POMC). The primary role of ACTH is to stimulate the adrenal cortex to produce glucocorticoids, principally cortisol, and to a lesser extent adrenal androgens. ACTH does not directly regulate electrolyte balance, which is mainly controlled by the renin–angiotensin system and aldosterone.

Synthesis and regulation occur within the hypothalamic–pituitary–adrenal axis. Corticotropin-releasing hormone (CRH), often with arginine vasopressin (AVP), is released from the hypothalamus and stimulates ACTH secretion. Cortisol produced by the adrenal cortex exerts negative feedback on both the pituitary and hypothalamus, reducing ACTH and CRH release. ACTH release follows a circadian rhythm, with peaks in the early morning, and can be increased by stress, illness, hypoglycemia, and physical exertion.

Mechanistically, ACTH binds to the melanocortin 2 receptor (MC2R) on adrenal cortical cells, activating the adenylate cyclase–cAMP signaling pathway. This promotes adrenal steroidogenesis and adrenal cortex growth. ACTH also promotes the growth and maintenance of the adrenal cortex.

Clinically, synthetic ACTH (cosyntropin) is used in diagnostic testing to assess adrenal reserve via the ACTH stimulation test. Abnormal ACTH and cortisol patterns help diagnose primary versus secondary adrenal insufficiency and other disorders such as Cushing’s disease (pituitary ACTH excess) or ectopic ACTH production. See also CRH, POMC, and the hypothalamic–pituitary–adrenal axis.