The ACTH test measures the amount of adrenocorticotropic hormone (ACTH) in your blood. This hormone is produced by the pituitary gland and helps control the production of cortisol, a hormone that helps regulate your body’s stress response. The test is used to diagnose disorders such as Cushing’s syndrome, Addison’s disease, and hypopituitarism. For this test, you MUST get your blood drawn between 7 and 10 am.