COMPARISON OF ORAL AND INTRAVENOUS DEXAMETHASONE SUPPRESSION TESTS IN THE DIFFERENTIAL DIAGNOSIS OF CUSHING'S SYNDROME

In seven cases of proven Cushing's syndrome, the intravenous infusion of dexamethasone at a rate of 1 mg/h for a period of 5 hours readily distinguished pituitary dependent Cushing's syndrome from other causes of Cushing's syndrome. Thus the 5 h – iv dexamethasone test may give the same differential diagnostic information as the classical oral dexamethasone suppression test of Liddle. The test is quick to perform, obviates the need for accurate urine collections and is not influenced by variations in the intestinal absorption of the glucocorticoid.