A rapid screening test for Cushing's syndrome.

A combination test consisting of two parts, a single dose of dexamethasone and a (1-24) ACTH injection, has been used for the diagnosis of Cushing's syndrome. The test was performed by administering 1 mg dexamethasone orally at 11 p.m. on the first day and 25 IU synthetic ACTH i.v. at 8 a.m. on the second day. Plasma cortisol was determined at 8 a.m. on the first and second day and 1-1/2 and 2 hours after the ACTH injection. The test was performed in 33 patients with Cushing's syndrome and in 114 controls without adrenal disease. After dexamethasone administration alone, cortisol values frequently overlapped between patients with Cushing's syndrome and controls. The validity of the test was considerably improved by adding ACTH stimulation. The test procedure is recommended as a screening test for Cushing's syndrome in ambulatory practice.