The ACTH stimulation test (also called the cosyntropin test or tetracosactide test) is a medical test usually ordered and interpreted by endocrinologists to assess the functioning of the adrenal glands stress response by measuring the adrenal response to adrenocorticotropic hormone (ACTH).[1][2] ACTH is a hormone produced in the pituitary gland that stimulates the adrenal glands to release cortisol.