Glucagon

Glucagon is a hormone secreted by the pancreas, which stimulates the breakdown of glycogen or stored body fat and the release of glucose by the liver for energy. It works in direct opposition to insulin. Liver glucose is freed when the blood sugar level drops to around 70 milligrams/100 milligrams of blood. Exercise and starvation both increase glucagon levels, as does the presence of amino acids in the blood after a high protein meal.