Corticotropin-releasing hormone testing in pituitary disease

The corticotropin-releasing hormone (CRH) test has been examined in many disorders of pituitary function, but its only clinical use is in the differential diagnosis of Cushing's syndrome. The CRH test is helpful for separating adrenocorticotropin (ACTH)-dependent causes from ACTH-independent causes of Cushing's syndrome and in separating pituitary sources of ACTH secretion from ectopic sources. In addition, the CRH test can reveal preoperatively the intrapituitary location of the microadenoma in most cases of Cushing's syndrome. Finally, the CRH test may give an early indication of failed surgery in cases that otherwise would meet the criteria for a cure.