glukagón

Glukagón, known in English as glucagon, is a peptide hormone produced by the alpha cells of the pancreatic islets. It is a key counterregulatory hormone that raises blood glucose levels when insulin is low, supporting energy supply during fasting, exercise, or stress. In humans, glucagon is encoded by the GCG gene and consists of 29 amino acids. After secretion, it acts on hepatic glucagon receptors, a G protein–coupled receptor, to initiate signaling that increases blood glucose.

Mechanism and actions: Glucagon activates adenylate cyclase through its receptor, increasing intracellular cAMP and triggering protein kinase A. This leads to activation of hepatic glycogen phosphorylase and inhibition of glycogen synthase, promoting glycogenolysis and gluconeogenesis. The hormone also promotes ketogenesis and lipolysis in the liver and supports amino acid uptake for gluconeogenesis. Its actions are most prominent in the liver, the primary organ for maintaining euglycemia during fasting.

Regulation: Secretion is stimulated by hypoglycemia, certain amino acids (notably alanine and arginine), and sympathetic activity; it is inhibited by hyperglycemia, insulin, and somatostatin. Glucagon works in concert with other counterregulatory hormones such as epinephrine, cortisol, and growth hormone, especially during prolonged fasting or stress.

Clinical use and context: Glucagon is used clinically to treat severe hypoglycemia, particularly when intravenous glucose is not immediately available. It is administered by injection or, in some cases, as a nasal spray. Recombinant forms are used in medical settings, and glucagon kits are common for emergency management of hypoglycemic events.

Biological context: Glucagon is produced from proglucagon; in the pancreas it yields glucagon, while in the intestine additional peptides derived from proglucagon, such as GLP-1 and GLP-2, contribute to other metabolic roles.