Adrenal dysfunction: test strategies for diagnosis.

The best way to detect Cushing's syndrome is to measure urinary free cortisol and to conduct a 1-mg dexamethasone suppression test. The best way to distinguish among the varieties of Cushing's syndrome is to measure plasma adrenocorticotropic hormone (ACTH). Urinary 17-ketosteroid and plasma testosterone determinations are the most useful tests for finding the cause of virilization. Short ACTH stimulation is the test of choice to detect adrenal insufficiency.