glucagone

Glucagone, commonly spelled glucagon in English, is a peptide hormone produced by the alpha cells of the pancreatic islets. The term glucagone is used in some languages as an alternate spelling. The hormone consists of 29 amino acids encoded by the GCG gene. Its principal role is to raise blood glucose levels when they fall, acting as a counterregulatory hormone to insulin.

Glucagon exerts its effects by binding the glucagon receptor on hepatocytes and other tissues. This receptor is Gs-coupled; activation raises intracellular cyclic AMP and activates protein kinase A. The result is increased hepatic glucose production by glycogenolysis and gluconeogenesis and, during fasting, enhanced lipolysis in adipose tissue. Glucagon also inhibits glycolysis in the liver to favor glucose output.

Secretion is stimulated by hypoglycemia, amino acids, and sympathetic activity; it is suppressed by high glucose and insulin. Clinically, glucagon is used to treat severe hypoglycemia, particularly when oral carbohydrate intake is not possible, administered as intramuscular or intravenous injections; a nasal glucagon form is also available. It may be used to counteract beta-adrenergic blocker overdose and as a diagnostic aid in certain pancreatic tests.