IGF1 and Hypoinsulinemia: Finally, our observations in small-bodied RasGrf1 KO mice of hypoinsulinemia, reduced pancreatic beta cell mass, and defective activation of Ras signaling after stimulation of isolated islet cells with IGF1, are also strongly indicative of an essential role of RasGrf1 in beta cell proliferation and neogenesis [17, 26].