Corticotropin, or Adrenocorticotropic Hormone (ACTH), is a 39 amino-acid compound formed form the cleavage of POMC (pro-opiomelanocortin) in the anterior pituitary.
ACTH stimulates the secretion of glucocorticoids, mineralocorticoids, and androgens—all from the adrenal cortex. ACTH binds to receptors on the adrenal cortex and induces steroidogenesis using cAMP.
Mediated through neural influences by means of a complex of hormones, the most important of which is CRH (corticotrophin-releasing hormone).
Diurnal rhythmicity of CRH causes a peak before awakening and a decline as the day progresses, and causes similar changes in the blood levels of cortisol.
Many stresses stimulate also ACTH, including physical, emotional, and chemical stresses.
Two mechanisms of feedback regulate feedback: "fast feedback" is sensitive to the rate of change in cortisol levels, whereas "slow feedback" is sensitive to the absolute cortisol level.