Research brief · 2026-09-09
What Is GLP-1, the Hormone Your Gut Already Makes?
GLP-1 was a hormone long before it was a headline. The name stands for glucagon-like peptide-1, and it is a short peptide of roughly thirty amino acids cut from a larger parent protein called proglucagon. The cells that make it, called L cells, sit in the lining of the small intestine and colon and release it into the blood within minutes of a meal.
Drucker's 2018 review in Cell Metabolism summarizes what the hormone does once released. In the pancreas, it prompts insulin release, but in a glucose-dependent way: the effect is strong when blood sugar is high and fades when it is normal. It suppresses glucagon, the hormone that pushes the liver to release sugar. It slows gastric emptying, so a meal leaves the stomach more gradually. And through receptors in the brainstem and hypothalamus, it reduces appetite. Holst's 2007 review in Physiological Reviews describes the same actions and adds the hormone's defining weakness: the enzyme DPP-4 inactivates natural GLP-1 within about two minutes of release.
That two-minute clock is why the natural hormone was never a medicine. Semaglutide and liraglutide are prescription medications engineered from GLP-1's structure to resist DPP-4 and stay in circulation for hours to days. They are FDA-approved for type 2 diabetes and for chronic weight management in specific populations. What they do is hold the receptor's signal on for far longer than a meal ever would, which is also why their effects and side effects differ from anything the natural hormone produces.
The limit is that the native hormone is a short meal signal, and most of what is known about long-term GLP-1 receptor activation comes from trials of the medications, not from the hormone itself. Whether any of those medications is appropriate for a given person is a physician's decision.
Sources
- Drucker DJ, Mechanisms of Action and Therapeutic Application of Glucagon-like Peptide-1
- Cell Metabolism 2018
- Holst JJ, The physiology of glucagon-like peptide 1
- Physiological Reviews 2007
- Lau JL, Dunn MK, Therapeutic peptides: Historical perspectives, current development trends, and future directions
- Bioorganic & Medicinal Chemistry 2018
Peptide Proof reports what studies found. We do not give medical advice, dosing guidance, or treatment recommendations.