ACTH, Plasma – 004440

Adrenocorticotropic hormone (ACTH), or corticotropin, is a peptide hormone consisting of 39 amino acids. It is produced in the anterior pituitary of the brain as part of the precursor molecule pro-opiomelanocortin (POMC). Tissue-specific cleavage results in ACTH and a range of related peptides.^1,4

ACTH stimulates formation and secretion of glucocorticoids (especially cortisol) by the adrenal cortex. The glucocorticoid production is regulated by various factors.^5-8 After stimulation (eg, by physical effort or by the internal body clock), the hypothalamus secretes CRH (corticotropin-releasing hormone). CRH acts on the pituitary, which in turn synthesizes and secretes ACTH. Finally, ACTH stimulates secretion of the glucocorticoids by the adrenals. High concentrations of glucocorticoids in the blood inhibit secretion of CRH and ACTH via a negative feedback mechanism.