The Dexamethasone-Suppressed Corticotropin-Releasing Hormone Stimulation Test Differentiates Mild Cushing’s Disease from Normal Physiology

The dexamethasone-suppressed CRH test (Dex-CRH test) differ-entiates patients with Cushing’s syndrome (CS) from those with pseu-do-Cushing states, who have decreased ACTH responses to CRH because of negative feedback exerted by chronic hypercortisolism. Normal subjects, however, have not been studied with the Dex-CRH test, raising concern that this test might not separate patients with CS from patients with normal adrenal function. To determine whether the criterion that separates CS from pseudo-Cushing states also would differentiate patients with Cushing’s disease (CD) from individuals with eucortisolism, we studied 20 healthy volunteers dur-ing low-dose (2 mg/day) dexamethasone suppression, and then during the Dex-CRH test (CRH stimulation test performed 2 h after com-pletion of low-dose dexamethasone suppression), and contrasted their results with those of 20 patients with surgically proven mild C