Cushing's disease: megadose dexamethasone suppression in a case refractory to medical therapy.

A patient with Cushing's disease failed to show complete suppressibility of adrenal function with conventional "high" doses of dexamethasone (8 mg per day). Higher doses were required to achieve suppression. Pituitary irradiation and medical therapy (cyproheptadine, metyrapone, and aminoglutethimide) failed to control the disease, necessitating bilateral adrenalectomy. The diagnostic and therapeutic implications of megadose dexamethasone suppression have not been clearly addressed in the medical literature. It is possible that adrenal suppression achieved only with unconventionally high doses of steroids may be predictive of refractoriness to nonsurgical therapy.