Overnight Dexamethasone Suppression Test

ACTH Suppression Test, Cortisol Suppression Test, Dexamethasone Suppression Test (DST), DST (Dexamethasone Suppression Test)

Test Overview

The overnight dexamethasone suppression test checks to see how taking a corticosteroid medicine (called dexamethasone) changes the levels of the hormone cortisol in the blood. This test checks for a condition in which large amounts of cortisol are produced by the adrenal glands (Cushing's syndrome).

Normally, when the pituitary glands make less adrenocorticotropic hormone (ACTH), the adrenal glands make less cortisol. See an illustration of the pituitary gland or the adrenal glands. Dexamethasone, which is like cortisol, decreases the amount of ACTH released by the pituitary gland, which in turn decreases the amount of cortisol released by the adrenal glands.

After taking a dose of dexamethasone, cortisol levels often stay abnormally high in people who have Cushing's syndrome. Occasionally other conditions (such as major depression, alcoholism, stress, obesity, kidney failure, pregnancy, or uncontrolled diabetes) can keep cortisol levels from decreasing after taking a dose of dexamethasone.

The night before the blood test, you will take a pill containing dexamethasone. The next morning, the cortisol level in your blood will be measured. If your cortisol level remains high, Cushing's syndrome may be the cause.

Occasionally an ACTH test may be done at the same time as the cortisol test.

	Go to top of page	Go to next section
Author:	Sydney Youngerman-Cole, RN, BSN, RNC	Last Updated: August 3, 2006
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism
© 1995-2008 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.