The ACTH stimulation test measures how well the adrenal glands respond to adrenocorticotropic hormone (ACTH). ACTH is a hormone produced in the pituitary gland that stimulates the adrenal glands to release a hormone called cortisol. The man-made form of ACTH is called cosyntropin.
How the Test is Performed
The test is done the following way:
- Your blood is drawn.
- The lab then checks the cortisol level in the blood sample.
- You then receive a shot (injection) of cosyntropin.
- After either 30 minutes or 60 minutes, depending on how much cosyntropin you receive, your blood is drawn again.
- The lab rechecks the cortisol level in the second blood sample.
How to Prepare for the Test
You may need to limit activities and eat foods that are high in carbohydrates 12 to 24 hours before the test. You may be asked to fast for 6 hours before the test. Sometimes, no special preparation is needed.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or slight bruising. This soon goes away.
An increase in cortisol after stimulation by ACTH is normal. Cortisol level after ACTH stimulation should be higher than 18 to 20 micrograms per deciliter (mcg/dL), depending on the dose of cosyntropin used.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your doctor about the meaning of your specific test results.
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Tests of adrenal reserve; Cortrosyn stimulation test
Guber HA, Farag AF. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds.Henry's Clinical Diagnosis and Management by Laboratory Methods
Schroeder E, Wang CCL. Adrenal insufficiency. In: McDermott MT, ed.Endocrine Secrets.
Stewart PM, Krone NP. The adrenal cortex. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds.Williams Textbook of Endocrinology.
Update Date 11/7/2013
Updated by: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.