Corticotropin-releasing factor (CRF) stimulation test in normal subjects and patients with Cushing's syndrome

The hormonal responses to human corticotropin-releasing factor (hCRF) were investigated in 6 normal subjects, 13 patients with Cushing's disease (8 with diffuse bilateral hyperplasia and 5 with nodular hyperplasia) and one patient with Cushing's syndrome due to an adrenal adenoma. hCRF (100 micrograms i.v.) was a potent stimulant of ACTH and cortisol in normal subjects. Patients with Cushing's disease due to diffuse hyperplasia showed variable ACTH and cortisol responses to hCRF. In both normal subjects and in patients hCRF consistently stimulated serum aldosterone levels. Patients with nodular hyperplasia had extremely suppressed plasma ACTH levels and no responses of ACTH, cortisol and aldosterone to hCRF like in the patient with adrenal adenoma. Our results suggest that hCRF-stimulation test may be a useful tool for differentiating pituitary and adrenal forms of Cushing's syndrome.