Cushing's disease: growth hormone response to hypoglycemia after correction of hypercortisolism

Growth hormone responses to insulin-induced hypoglycemia were studied in 17 patients with inactive Cushing's disease. A normal GH rise was found in 9 of 9 patients without evidence of progressive pituitary tumor after bilateral adrenalectomy and 3 of 4 patients after correction of hypercortisolism by transsphenoidal removal of pituitary microadenomas. In contrast, 3 of 4 patients with Nelson's syndrome had impaired GH responsiveness to hypoglycemia. These results show that GH responsiveness is normal in the majority of patients with inactive Cushing's disease and do not support the concept of a primary hypothalamic or central nervous system abnormality of GH regulation in Cushing's disease.