Adrenocorticotropic hormone (ACTH), also known as corticotropin, is a cleavage product from a larger precursor proopiomelanocortin (POMC). This 39 amino acid-peptide hormone is produced in the anterior pituitary gland upon stimulation by the corticotropin releasing hormone from the hypothalamus in response to stress. It stimulates the secretion of steroid hormone, specifically glucocorticoids in the adrenal cortex by acting through a cell membrane receptor (ACTH-R). In mammals, the action of ACTH is limited to those areas of the adrenal cortex in which the glucocorticoid hormones cortisol (hydrocortisone) and corticosterone are formed. ACTH has little control over the secretion of aldosterone, the other major steroid hormone from the adrenal cortex.