What Is an Incretin?

1. What Is an Incretin?

An incretin is a hormone secreted by the gut in response to food, especially carbohydrates, that increases the release of insulin from the pancreas. The key feature is that incretins boost insulin in a glucose-dependent way: they have the strongest effect when blood sugar is rising after a meal, and much less effect when blood sugar is already low.

The two main human incretins are GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). If you have read about what a GLP-1 is, you have already met one half of the incretin system.

2. The Incretin Effect

The reason scientists know incretins exist comes from a simple experiment. If you give someone glucose by mouth, their insulin response is much larger than if you infuse glucose into a vein at a rate adjusted to reproduce exactly the same blood-glucose curve, the isoglycaemic infusion Nauck and colleagues used in 1986. Matching the glucose curve, not the glucose amount, is what isolates the gut’s contribution. That gap is called the incretin effect, and it exists because eating triggers gut hormones that the intravenous route bypasses.

In healthy people, the incretin effect can account for a large share of the insulin released after a meal. In type 2 diabetes, the incretin effect is blunted, which is part of why incretin-based medicines became such an active area of research.

3. GLP-1 vs GIP: The Two Incretins

Both GLP-1 and GIP are released by specialized cells in the gut lining after eating, and both raise insulin. They differ in their other jobs.

GLP-1’s appetite and stomach-emptying effects are a big reason the GLP-1 pathway became central to weight management, not just blood-sugar control. For the receptor-language side of this, see GLP-1 vs GLP-2 vs GLP-3.

4. Incretins vs Incretin-Based Medicines

This is the distinction that trips people up. The hormones GLP-1 and GIP are incretins. The medicines people take are not incretins themselves; they are incretin-based therapies that imitate or amplify those hormones, usually by activating the same receptors and resisting the rapid breakdown that natural incretins undergo.

• A natural incretin is a hormone your body makes.
• An incretin mimetic or receptor agonist is a drug designed to act like it.
• “Incretin-based therapy” is the umbrella term for these medicines.

5. How the Drug Classes Map to the Incretins

Once you know the incretins, the alphabet soup of modern molecules becomes a simple grid based on which receptors each one targets.

Note that the GLP-1/glucagon and triple agonists add a glucagon target. Glucagon is a related metabolic hormone but is not an incretin, which is why those drugs are described as incretin-based plus a glucagon component.

6. What Is Not an Incretin

Two hormones come up constantly in this space but are not incretins:

• Glucagon: a pancreatic hormone that raises blood sugar and, via its receptor, increases energy expenditure and liver fat oxidation. Targeted by drugs like survodutide and efinopegdutide, but not an incretin.
• Amylin: a hormone co-released with insulin that promotes fullness. Targeted by drugs like cagrilintide, eloralintide, and petrelintide. See What Is Pramlintide? for the hormone and the first drug built on it.

7. Why This Matters

Understanding incretins turns a confusing list of brand names and code names into a small set of mechanisms. Almost every weight or diabetes molecule making headlines is built on the incretin system, either copying one incretin, combining two, or adding a non-incretin hormone like glucagon or amylin on top.

• Incretin = a gut hormone (GLP-1 or GIP) that raises insulin after eating.
• Incretin effect = why oral glucose beats IV glucose at triggering insulin.
• Incretin-based therapy = medicines that mimic or amplify these hormones.
• Glucagon and amylin = related hormones that are not incretins.

8. What Is an Incretin FAQ

• What is an incretin in simple terms?

  An incretin is a hormone your gut releases after you eat that tells the pancreas to release more insulin. Because it acts mainly when blood sugar is rising, it helps the body handle a meal. The two main human incretins are GLP-1 and GIP.

• What is the incretin effect?

  The incretin effect is the observation that glucose taken by mouth triggers a much larger insulin response than an intravenous glucose infusion matched to the same blood-glucose curve. The difference is caused by incretin hormones released from the gut during digestion.

• Are GLP-1 drugs incretins?

  GLP-1 receptor agonist medications are not incretins themselves; they are incretin-based therapies that mimic the natural incretin hormone GLP-1 by activating the same receptor. The term incretin refers to the body's own hormones.

• Is glucagon an incretin?

  No. Glucagon is a related pancreatic hormone, and some newer drugs target the glucagon receptor alongside GLP-1, but glucagon is not classified as an incretin. The recognized human incretins are GLP-1 and GIP.

• What is the difference between GLP-1 and GIP?

  Both are incretins released by the gut after eating. GLP-1 also slows gastric emptying and reduces appetite, which is central to weight-related effects. GIP is the other major incretin, and some drugs target both receptors at once.

9. Sources