Glucagon is a 29 amino acid peptide hormone produced by alpha cells in the pancreas. It raises glucose and fatty acid levels in the bloodstream and is the main catabolic hormone. Glucagon is secreted in response to low blood glucose, protein ingestion, and exercise, and is inhibited by carbohydrate ingestion. Glucagon acts on the liver to stimulate glycogen breakdown and gluconeogenesis to prevent dangerous drops in blood glucose and maintain stable levels.