Peptide glossary
Incretin
Gut hormones, GLP-1 and GIP, that amplify insulin release after a meal; the basis of the semaglutide, tirzepatide and retatrutide class.
Incretins are hormones released by the gut in response to food that cause the pancreas to release more insulin than the same amount of glucose given intravenously would provoke. The effect was named before the hormones were identified; the two that account for it are GLP-1 and GIP. Because their insulin effect is glucose-dependent, they raise insulin when blood sugar is high and largely stop when it is not, which is what makes the class attractive compared with insulin itself.
The incretin class of compounds is built by taking one or both hormones and re-engineering them for a long half-life. Semaglutide is a GLP-1 analogue. Tirzepatide activates both incretin receptors. Retatrutide adds the glucagon receptor, which is not an incretin but complements them. All three are dosed once weekly by subcutaneous injection in the trial literature.
The GLP-1 receptor agonists comparison is the overview of the class; the comparison pages set the three compounds side by side.
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Research & educational use only. Definitions are informational and not medical advice. Products are supplied for laboratory research and are not for human use.