Overnight Dexamethasone Suppression Test: What To Think About

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What To Think About

• An overnight dexamethasone suppression test is used to check for Cushing's syndrome. An abnormal test result may mean that further testing is needed to identify Cushing's syndrome. Likewise, a normal test result means that you do not have Cushing's syndrome. Because Cushing's syndrome can be hard to diagnose, an endocrinologist should be consulted if test results are uncertain or if the test results do not help explain your symptoms.
• Sometimes a more extensive dexamethasone suppression test may be done. For this test, you will take up to 8 dexamethasone pills over 2 days and then cortisol levels in your blood and urine will be measured.
• Some doctors think that a 24-hour urine free cortisol test is more accurate than an overnight dexamethasone suppression test. Like an overnight dexamethasone suppression test, a 24-hour urine free cortisol test is used to look for Cushing's syndrome. For more information, see the medical test Cortisol in Urine.
• An adrenocorticotropic hormone (ACTH) test may be done at the same time as the cortisol test. For more information, see the medical test Adrenocorticotropic Hormone.

Last updated:	June 26, 2008
Author:	Bets Davis, MFA
Reviewed By:	Caroline S. Rhoads, MD - Internal Medicine, David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism
Editors:	Susan Van Houten, RN, BSN, MBA, Tracy Landauer