Question: What is an ACTH Stimulation Test and what is it used for?

Answer: An ACTH stimulation test is most commonly used in patients with Cushing’s Syndrome many months after surgery to determine whether their hypothalamic-pituitary-adrenal axis is recovering and whether it is therefore safe to discontinue their steroid medications. It is a 1 hour test in which an injection of synthetic ACTH is administered and cortisol levels are measured at the start of the test, and at 30 and 60 minutes. If the cortisol rises to 18 or higher, the patient is making enough cortisol on their own to discontinue steroid medication. There are other uses of this test in other adrenal disorders.

By Dr. Beverly MK. Biller MD (Spring 1995)