Insulin's counterpart — and the 'third receptor' behind multi-agonist metabolic peptides.
Part of the Metabolic & GLP-1 peptides cluster
Overview
Glucagon is a 29-amino-acid peptide hormone from pancreatic alpha cells that raises blood glucose, opposing insulin. It is the archetypal counter-regulatory hormone and, more recently, the glucagon receptor has become a deliberate target in triple-agonist peptides such as retatrutide.
Source & context
Biological / chemical source: Pancreatic alpha cells
Primary research or clinical context: Endogenous hormone; approved emergency medicine and a receptor target in dual/triple agonist research
Physiology
When blood glucose falls, alpha cells release glucagon, which signals the liver to break down glycogen and generate new glucose. It shares a common ancestral gene family with GLP-1, GIP and secretin, and all of these act through related class-B G-protein-coupled receptors — a tidy illustration of peptide-hormone evolution.
Why it appears in modern peptide research
For decades glucagon was viewed only as insulin's opposite. Newer engineered peptides intentionally add glucagon-receptor activity to incretin agonism, aiming to influence energy expenditure alongside glucose and appetite signaling. This is why glucagon biology now appears throughout discussions of dual and triple agonists.
Sequence
One-letter sequence commonly cited for Glucagon (educational; isoforms and modifications may differ):
HSQGTFTSDYSKYLDSRRAQDFVQWLMNT
Residues plotted ~100° apart around an α-helix — clustering of one color reveals an amphipathic face.
FAQ about Glucagon
What is Glucagon?+
Glucagon is a 29-amino-acid peptide hormone from pancreatic alpha cells that raises blood glucose, opposing insulin. It is the archetypal counter-regulatory hormone and, more recently, the glucagon receptor has become a deliberate target in triple-agonist peptides such as retatrutide.
Is Glucagon an approved medicine?+
Glucagon is discussed here as a research / educational topic. Endogenous hormone; approved emergency medicine and a receptor target in dual/triple agonist research. This is not medical advice.
What is the typical length of Glucagon?+
Glucagon is commonly described as approximately 29 amino acids (Hormone).