Clinical Applications of Corticotropin-Releasing Factor

Ovine and human corticotropin-releasing factors (CRF) have similar potencies in causing adrenocorticotropic hormone (ACTH) and cortisol secretion in normal humans. Using long-acting ovine CRF (1 µg/kg body weight as an intravenous bolus), we tested patients with Cushing's syndrome, adrenal insufficiency, and psychiatric conditions with mild hypercortisolism. Over 95% of hypercortisolemic patients with a pituitary adenoma responded with increases in plasma ACTH and cortisol concentrations; patients with the ectopic ACTH syndrome had no ACTH or cortisol responses; patients with ACTH-independent hypercortisolism of adrenal origin had low or undetectable plasma ACTH concentrations before and after CRF without any cortisol response. The differences in responses of patients with adrenal insufficiency of primary, pituitary, or suprapituitary type likewise suggest value of the CFR test in their differential diagnosis. The responses in the psychiatric patients should permit differentiation between Cushing's syndrome and hypercortisolism of psychiatric origin.