Glucagon and the a Cell: Physiology and Pathophysiology

IN this review we examine the role of glucagon, a polypeptide produced by the islets of Langerhans and a biologic antagonist of insulin. The effects of glucagon balance those of insulin so that fluctuations in blood sugar levels in response to sudden changes in fluxes of fuels are prevented. By definition, relative hyperglucagonemia is present in all forms of diabetes in which glucose production exceeds glucose disposal and thus causes “endogenous hyperglycemia”; in the absence of glucagon-like biologic activity the massive hepatic overproduction of glucose and ketones observed in uncontrolled diabetes does not occur, even in the total absence of. . .