In ob/ob mice, although there was no change in the weight of the mice, glucose and insulin levels decreased in the hours after LEP replacement,16 whereas the administration of LEP antagonists increased blood glucose and insulin levels before changes in body weight.17 Intravenous injections of LEP have been shown to normalize hyperglycemia and hyperinsulinemia and improve insulin sensitivity in lean mice.18 The gene discussed is LEP; the disease is hyperinsulinism.