The dexamethasone supression test is designed to diagnose and differentiate among the various types of Cushing's syndrome and other hypercortisol states.

Dexamethasone is an exogenous steroid that can provide negative feedback to the hypothalamus and anterior pituitary to suppress the secretion of ACTH. The test is given at low and high doses of Dexamethasone and the levels of cortisol are measured to obtain the results. A normal result is decrease in cortisol levels upon administration of low-dose dexamethasone. Results indicative of Cushing's disease involve no change in cortisol on low-dose dexamethasone, but inhibition of cortisol on high-dose dexamethasone. If the cortisol levels are unchanged by low and high-dose dexamethasone then a cortisol secreting adrenocortical tumor is highly suspect. Chemical pathology