LAB TEST
Dexamethasone suppression test
The dexamethasone suppression test measures whether cortisol secretion by the adrenal gland can be suppressed. It can also help assess the reason for an excess of cortisol in your body such as if it is due to an excess of adrenocorticotrophic hormone (ACTH) secretion by the pituitary.
How the Test is Performed
During this test, you will receive dexamethasone. This is a strong man-made (synthetic) glucocorticoid medicine. Afterward, your blood is drawn so that the cortisol level in your blood can be measured. There are two different types of dexamethasone suppression tests: low dose and high dose. Each type can either be…
How to Prepare for the Test
Your provider may tell you to stop taking certain medicines that can affect the test, including: Antibiotics Anti-seizure medicines Medicines that contain corticosteroids, such as hydrocortisone, prednisone Estrogen Oral birth control (contraceptives) Water pills (diuretics)
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.
Why the Test is Performed
This test is done when your provider suspects that your body is producing too much cortisol. It is done to help diagnose Cushing syndrome and identify the cause. The low-dose test can help tell whether your body is producing too much ACTH. The high-dose test can help determine whether the problem is in the pituitary…
Normal Results
Cortisol level should decrease after you receive dexamethasone. Low dose: Overnight -- 8 a.m. plasma cortisol lower than 1.8 micrograms per deciliter (mcg/dL) or 50 nanomoles per liter (nmol/L) Standard -- Urinary free cortisol on day 3 lower than 10 micrograms per day (mcg/day) or 280 nmol/L High dose: Overnight --…
What Abnormal Results Mean
An abnormal response to the low-dose test may mean that you have abnormal release of cortisol (Cushing syndrome). This could be due to: Adrenal tumor that produces cortisol Pituitary tumor that produces ACTH Tumor in the body that produces ACTH ( ectopic Cushing syndrome ) The high-dose test can help tell a pituitary…
Risks
There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Taking blood from some people may be more difficult than from others. Other risks associated with having blood drawn are slight, but may include: Excessive…
References
Bertholf RL, Cooper M, Winter WE. Adrenal cortex. In: Rifai N, Chiu RWK, Young I, Burnham CD, Wittwer CT, eds. Tietz Textbook of Laboratory Medicine . 7th ed. Philadelphia, PA: Elsevier; 2023:chap 56. Guber HA, Oprea M, Russell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical…
This is a summary. Read the full article at www.ucsfbenioffchildrens.org (reviewed 12/05/2023).
This page is general information and is not medical advice. It does not replace a registered doctor, and it is not a prescription or a recommendation to use any medicine or test. Prices are listed prices and may change. Always follow the advice of your doctor or pharmacist.