From single to triple agonist
In ten years this family went from one receptor to three. Each step added a route, and every route does something different with energy.
Three generations in a row
| Substance | GLP-1 | GIP | Glucagon |
|---|---|---|---|
| Semaglutide | yes | no | no |
| Tirzepatide | yes | yes | no |
| Retatrutide | yes | yes | yes |
| Mazdutide | yes | no | yes |
Mazdutide stands out in that table: it skips GIP and takes glucagon instead. That is not a mistake but a route of its own, built on oxyntomodulin, a natural hormone that already fits those two receptors.
What the first receptor does
GLP-1 curbs appetite, slows the stomach and drives insulin when needed. Semaglutide is the best known example: a chain resembling GLP-1, with two modifications that make it last days instead of minutes.
What the second adds
GIP is the second incretin. Tirzepatide hits both. In research that combination goes further than GLP-1 alone, but exactly why is not settled. There are signs that GIP acts directly on fat tissue and that it dampens the nausea belonging to the GLP-1 route, leaving more room before things get uncomfortable.
An agonist is a substance that fits a receptor and switches it on, just like the natural hormone. An antagonist also fits but sets nothing in motion and occupies the spot. Dual agonist therefore means: switches on two different receptors.
Why glucagon is the odd one out
GLP-1 and GIP both come from the gut and both lower blood sugar. Glucagon does the opposite: it comes from the pancreas and releases sugar from the liver. A substance that switches on GLP-1 and glucagon at once therefore looks like it is working against itself.
The thinking behind it is that glucagon does not only release sugar but also raises energy expenditure. So you press the accelerator and the brake together, expecting the GLP-1 part to keep blood sugar in check while the glucagon part raises burn. Whether that balance works out as intended is exactly what is being studied.
What this means for research
The more receptors a substance hits, the harder it becomes to attribute an observed effect to a route. With a single agonist you know what you are looking at. With a triple agonist the same result can come from three directions, or from an interplay you see in none of the three alone.
That is not an objection but a design choice in a study. It is also why the single agonists do not disappear from the literature: they remain the reference point everything else is measured against.
This site is made by the team behind Apex Bio Research, a Dutch supplier of research peptides with a certificate of analysis per batch.
Visit the shopThis site explains what the scientific literature says about peptides. It is not medical advice and not a set of instructions. The substances discussed here are research compounds: they are not approved for use in humans or animals. If you have a health question, see a doctor.
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