Glucagon (Thomsen J et al, 1972) is an important peptide hormone produced by the pancreas. It is released when the glucose level in the blood is low (hypoglycemia), causing the liver to convert stored glycogen into glucose and release it into the bloodstream. The action of glucagon is thus opposite to that of insulin. Glucagon, together with glucagon-like peptide 1 (GLP-1) and glucagon-like peptide 2 (GLP-2), are peptide hormones encoded by a single common prohormone precursor, proglucagon.The glucagon receptor (Lok S et al, 1994) plays a central role in regulating the level of blood glucose by controlling the rate of hepatic glucose production and insulin secretion. The activity of this receptor is mediated by coupling to Gs and q, which stimulate adenylyl cyclase and a phosphatidylinositol-calcium second messenger system respectively.