Glucagon increases plasma glucose levels by stimulation of glycogenolysis in the liver. After binding to a G-protein coupled receptor, the second messenger cAMP stimulates enzymes of glycogenolysis. The glucose is released by the liver and glucose blood levels rise.
Glucagon is indicated in cases of severe hypoglycemia after the use of blood glucose lowering drugs. One mg of glucagon should be injected intramuscularly or intravenously. When the patient is conscious again, he/she should take carbohydrate rich food.
I. Glucagon is used to treat insulin-induced hypoglycemia in type I diabetes patients.
II. Glucagon is still effective when the liver is out of glycogen reserves.
Extra info: Patients with type 1 diabetes mellitus, who use insulin, can develop hypoglycemia because of a too high dosage of insulin. In such a situation, glucagon can “reverse” the action of insulin. Glucagon converts glycogen into glucose. When the body is out of glycogen reserves, treatment with glucagon is not effective.