Endocrinology. A peptide hormone containing 39 amino acids, the first 24 of which are identical in all species and responsible for the biological activity. It is produced by the anterior pituitary gland induced by the corticotropin-releasing hormone (CRH) of the hypothalamus. ACTH stimulates the secretion of glucocorticoids of the adrenal cortex, influences the immunsystem and many metabolisms indirectly by corticosterone. The ACTH concentration depends on the circadian rhythm.