§ Glossary · biology

Glucagon

A pancreatic hormone that opposes insulin — raises blood glucose, promotes lipolysis and ketogenesis.

Glucagon is a 29-amino-acid peptide hormone secreted by pancreatic α-cells when blood glucose drops. It opposes insulin: stimulating hepatic glycogenolysis and gluconeogenesis to raise blood glucose, and promoting adipose lipolysis and hepatic ketogenesis during fasting. Glucagon receptor agonism is investigated in research literature for hepatic-fat reduction (the rationale behind retatrutide's third receptor arm). Therapeutic glucagon agonism is balanced against the diabetic-glucose-spike risk; co-agonism with GLP-1 / GIP (incretins) provides counter-regulatory cover.

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