An incretin is a gut-derived hormone that amplifies glucose-stimulated insulin secretion when nutrients arrive by the oral route. The term comes from the incretin effect: an oral glucose load produces a substantially larger insulin response than an intravenous infusion matched to give the same blood glucose curve. In healthy human physiology this gut-derived amplification accounts for roughly half to two-thirds of the insulin response to a meal.
The two incretins
Only two hormones meet the definition in humans. GIP is released from duodenal K-cells; GLP-1 is released from more distal L-cells. Both are class B GPCR ligands, both potentiate insulin secretion only when glucose is elevated — the glucose dependence that makes incretin biology attractive — and both are cleaved within minutes by dipeptidyl peptidase-4 at their penultimate alanine.
Why it matters
Every engineered analog in this category exists to defeat that DPP-4 clock. Substituting the cleavage site with Aib or a D-residue and adding a fatty-acid chain for albumin binding extends the half-life from minutes to days. Understanding which incretin receptor a research peptide engages, and at what relative potency, is the first question when selecting a comparator.
Related terms
GLP-1 receptor agonist · dual agonist · amylin. Browse GLP-1 and incretin peptides or the GLP-1 / incretin pathway hub.