A feature on A-Z Animals traces the origin of GLP-1 receptor agonist medications back to a peptide isolated from the venom of the Gila monster, the only venomous lizard native to the United States.

The peptide is Exendin-4, and the human hormone it resembles is GLP-1, which stimulates insulin production in the pancreas. Semaglutide, sold as Ozempic and Wegovy, belongs to the drug class that grew out of that resemblance, and the piece is careful to note that Gila monster venom is not an ingredient in any commercial GLP-1 medication.

A lizard that does not eat much

Heloderma suspectum reaches up to two feet, lives in dry desert and oak woodland across the southwestern deserts of North America, and spends most of its time in burrows. Fat deposits let it survive on three or four large meals a year, which turns out to be the biologically interesting part.

Unlike snakes, Gila monsters deliver venom through grooves in their lower teeth, working it into a wound by chewing. The reputation that followed was fierce enough that in 1891 a Tombstone physician, Dr. George Goodfellow, let himself be bitten to test it. He recovered fully after five days in bed in severe pain.

What John Eng noticed in 1990

Dr. John Eng, an endocrinologist at the Bronx Veterans Administration Center, was researching new hormones when he learned that certain reptile venoms caused the pancreas to enlarge. He also noticed that Gila monsters hold blood sugar steady through long stretches without food.

Analyzing the venom produced Exendin-4, which triggers insulin release and synthesis from pancreatic cells. The structural similarity to GLP-1 was close, but the durability was not: GLP-1 stays active for a few minutes, Exendin-4 for hours. That gap is the entire commercial story, and it eventually produced the derivative exenatide.

The scale now

The numbers the piece cites are striking. Eighteen percent of American adults have taken a GLP-1 at some point, around 12 percent are currently using one, and Ozempic generated roughly $9.1 billion in the first six months of 2026 alone.

Bottom line

The venom was a clue, not an ingredient. What it pointed to was a mechanism for steady blood sugar during long fasting, and the article's closing argument is the old one about dose separating medicine from poison.