The pancreatic islet is composed of multiple endocrine cells. Most of the work is focused on the beta-cell, presenting glucose control and diabetes as a unihormonal disorder. Contrary to this current approach, clinical data and animal experiments have shown that glucagon secretion by alpha-cells and somatostatin from delta-cells play a role in glucose control and are dysregulated in the pathogenesis of hyperglycemia in type 1 and type 2 diabetes. My laboratory has been exploring how insulin signaling regulates the function and mass of beta and alpha cells in vivo and the potential contribution of this process to the regulation of glucose homeostasis.