Glucagon

Glucagon is a peptide hormone made by pancreatic alpha cells. It raises blood glucose chiefly by stimulating the liver to release glucose and produce more.

Glucagon receptor: A G protein-coupled receptor that binds glucagon and activates signaling in target cells, especially liver cells. Binding starts the liver-cell signaling cascade that mobilizes glucose.
Pancreatic alpha cell: An endocrine cell in the pancreatic islets that secretes glucagon. These cells release glucagon when falling glucose or other signals call for it.
Glucagon therapy: The medical use of glucagon to raise blood glucose or treat selected drug overdoses. Injected or inhaled glucagon can treat severe hypoglycemia when oral sugar is impractical.
Somatostatin: A hormone that inhibits secretion of several other hormones, including glucagon and insulin. Pancreatic delta cells use it to restrain glucagon release locally.
G protein-coupled receptor: A cell-surface receptor that transmits signals by activating intracellular G proteins. The glucagon receptor belongs to this large signaling-receptor family.
Pancreatic islets: Clusters of endocrine cells in the pancreas that secrete hormones regulating metabolism. Alpha cells that make glucagon are embedded in these endocrine clusters.
Hypoglycemia: A condition in which blood glucose falls below the level needed for normal function. Glucagon is an emergency treatment because it can rapidly increase glucose.
Amylin: A peptide hormone co-secreted with insulin by pancreatic beta cells that slows gastric emptying and suppresses glucagon after meals. Its post-meal action helps oppose glucagon secretion and glucose appearance.
Cyclic adenosine monophosphate: A second messenger that relays signals inside cells and activates protein kinase A. Glucagon raises this messenger in liver cells to amplify its signal.
Liver: A large organ that processes nutrients, stores glycogen, and helps regulate blood chemistry. It is glucagon’s principal target for raising circulating glucose.

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