Tetracosactide (INN) (brand names Synacthen, Cortrosyn), also known as tetracosactrin (BAN) and cosyntropin (USAN), and the acetate ester, tetracosactide acetate (JAN) (brand names Cortrosina, Cortrosyn, Nuvacthen, Synacthen), also known as tetracosactrin acetate (BANM), is a synthetic peptide and analogue of adrenocorticotrophic hormone (ACTH) which is used clinically as a diagnostic agent.