Islet cell function and glucose homeostasis in hypopituitary dwarfism: Synergism between growth hormone and cortisone

Abstract

Detailed studies of islet cell function and glucose regulation were carried out in fourboys with idiopathic hypopituitary dwarfism to assess the relative importance of glucocorticoid and growth hormone deficiencies in the pathogenesis of hypoglycemia in this condition. Studies in each boy were done during a control period with no hormonal replacement and during three experimental regimens in which growth hormone alone, cortisone alone, and cortisone combined with growth hormone were administered. Combined cortisone-growth hormone therapy significantly raised blood sugar levels after overnight fasting and during fasting for prolonged periods, delayed the rate of glucose removal, decreased sensitivity to exogenous insulin, and resulted in augmentation of plasma insulin responses to intravenous administration of glucose, leucine, and tolbutamide. Thus improved islet cell function was associated with normalization of glucose homeostasis. When given separately, growth hormone and cortisone had smaller and less consistent effects. These findings are consistent with the clinical observation that treatment of hypopituitary patients with cortisone or growth hormone alone is usually ineffective in controlling hypoglycemic attacks. The synergism between cortisone and growth hormone on glucose homeostasis contrasts sharply with the antagonism of cortisone to the anabolic and growth-promoting actions of growth hormone.