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GLP-1

GLP-1 (glucagon-like peptide-1) is a hormone your gut already makes. It’s released from cells in your intestine after you eat, and it does several jobs at once: it tells your pancreas to release insulin, tells your liver to ease off producing sugar, slows how fast your stomach empties, and signals fullness to your brain. It’s part of the body’s normal “I’ve eaten, we’re good” system.

Why the medications borrow its name

The whole drug class — semaglutide, tirzepatide, liraglutide — works by mimicking this hormone. They’re called GLP-1 receptor agonists: “agonist” means they switch on the same receptors natural GLP-1 does. The catch with your own GLP-1 is that it breaks down in minutes. The medications are engineered to resist that breakdown, so a single injection keeps the signal going for a week instead of minutes.

What that means in practice

Everything people notice on treatment traces back to this one hormone’s amplified signal: earlier fullness and smaller meals (the appetite effect), quieter food noise (the brain effect), occasional nausea (the slowed stomach), and better blood sugar (the insulin effect). Understanding GLP-1 is the single fact that makes the rest of the vocabulary click into place.

Tirzepatide adds a second hormone, GIP, to the GLP-1 action — which is why it’s technically a dual agonist rather than a pure GLP-1 drug.