Petrosal Sinus Sampling with and without Corticotropin-Releasing Hormone for the Differential Diagnosis of Cushing's Syndrome

Measurement of adrenocorticotropin levels in plasma from the inferior petrosal sinuses of patients with Cushing's syndrome can distinguish adrenocorticotropin-secreting pituitary tumors (Cushing's disease) from other causes of the syndrome, principally ectopic adrenocorticotropin secretion from an occult tumor. However, it is unknown whether such measurement consistently identifies patients with Cushing's disease and whether testing with corticotropin-releasing hormone (CRH) enhances the value of the procedure.