ACTH is a 39-residue polypeptide with a molecular weight of 4540 Da. It is secreted from corticotropes in the anterior lobe (adenohypophysis) of the pituitary gland in response to cortocotrop-releasing hormone (CRH) released by the hypothalamus. ACTH is synthesized from pre-pro-opiomelanocortin (pre-POMC) The removal of the signal peptide during translation produces the 241-amino acid polypeptide POMC, which undergoes a series of post-translational modifications, such as phorphorylation and glycosylation, before it is proteolytically cleaved by endopeptidases to yield various polypeptide fragments with varying physiological activity.
ACTH is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological stress. It stimulates secretion of glucocorticoid steroid hormones from adrenal cortex cells, especially in the zona fasciculata of the adrenal gland. ACTH acts by binding to cell surface ACTH receptors, which are located primarily on adrenocortical cells of the adrenal cortex.