GLP-1 is a hormone your gut releases after you eat. It helps your body handle rising blood sugar and plays a part in appetite and fullness.
The name stands for glucagon-like peptide-1. It’s one example of a peptide acting as a messenger. Understanding that message makes it easier to see how GLP-1 medicines work, too.
A message from the gut
When food arrives, cells in your intestine release GLP-1. It belongs to a group of hormones called incretins, which help the pancreas respond to a meal by releasing insulin. Insulin then helps cells take up glucose from the blood.
NIDDK’s account of GLP-1 research traces how this connection between food, gut hormones, and blood sugar led to new medicines.
GLP-1 passes on its message by activating a receptor, a receiving point on a cell. When the hormone binds to it, that connection sets a response in motion.
Its insulin effect depends on blood sugar
GLP-1 helps increase insulin release when glucose is high. As glucose falls toward normal levels, that extra insulin response eases off.
An early study by Nauck and colleagues showed this in ten adults with type 2 diabetes. During a GLP-1 infusion, insulin rose and their elevated blood glucose fell. Once glucose reached the normal fasting range, insulin moved back toward its starting level, even while the infusion continued.
Researchers also saw lower glucagon, the hormone that tells the liver to release glucose. That gives GLP-1 another way to influence blood sugar.
Why it affects hunger
GLP-1 can slow the movement of food from the stomach into the intestine. It also acts through receptors in brain regions involved in appetite, as described in the FDA’s semaglutide prescribing information.
In a test-meal study by Flint and colleagues, 20 healthy men received GLP-1 or saline. With GLP-1, they felt fuller and ate less at lunch.
A smaller study using a shorter infusion found slower stomach emptying but no significant change in hunger or food intake. The timing and conditions differed. These experiments help explain why researchers measure stomach emptying and appetite separately: a change in one doesn’t always come with the same change in the other.
Why GLP-1 medicines last longer
Your body breaks down natural GLP-1 quickly. Its signal lasts only minutes, which helped inspire the development of medicines that stay active longer.
These medicines are called receptor agonists: they activate the receptor that GLP-1 uses. Semaglutide is one example. Its structure protects it from breakdown and helps it bind to albumin, a protein in the blood.
According to its FDA label, semaglutide has an elimination half-life of about a week. That means it takes roughly a week for the amount in the body to fall by half during elimination.
That’s the connection: a short-lived signal your body already uses, and medicines designed to act on the same receptor for longer.
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