An anterior pituitary hormone that stimulates the adrenal cortex and its production of CORTICOSTEROIDS. ACTH is a 39-amino acid polypeptide of which the N-terminal 24-amino acid segment is identical in all species and contains the adrenocorticotrophic activity. Upon further tissue-specific processing, ACTH can yield alpha-msh and corticotrophin-like intermediate lobe peptide (CLIP).