The physiological role of glucagon in glucose homeostasis has been investigated in animal models where glucagon signaling was blocked at the receptor level by either genetic or pharmacological means: Glucagon receptor knockout mice (Gcgr-/- mice) had lowered plasma glucose levels without exhibiting hypoglycemia [8, 9], whereas treating the animals with glucagon receptor antagonists reduced blood glucose levels in various rodent models [10, 11]. This evidence concerns the gene GCGR and Hypoglycemia.