WHAT IS DEXAMETHASONE SUPPRESSION TEST?
Screening test for Cushing’s disease and for depression. The test can be performed after administration of a low or high dose of dexamethasone or as an overnight test with a morning blood draw. Dexamethasone is a potent synthetic glucocorticoid that is used to test the integrity of the hypothalamic-pituitary-adrenal axis. When given to normal clients, it decreases the production of cortisol and other adrenal steroids through the usual feedback systems. In clients with Cushing’s disease or depression, there is no suppression of ACTH. The low test dose is for screening. If results are positive, a high-dose test is given to determine the cause of Cushing’s disease. If there is suppression with the high-dose test, it indicates a pituitary origin of the excess cortisol. If there is no suppression, it indicates an adrenal or ectopic tumour.