GLP-1, GIP and Glucagon: What the Receptor Names Mean
Product pages in this category are full of words like receptor, agonist and dual agonist. This guide explains what each of them means in plain terms, shows how semaglutide, tirzepatide and retatrutide differ, and explains why hitting more receptors is not automatically better. Supplied for in vitro research purposes only.
4 minute read
What Are GLP-1, GIP and Glucagon?
They are three natural hormones your body already makes. Each one has its own docking point on the surface of cells, called a receptor.
Think of a receptor as a lock and the hormone as the key. When the key turns, the cell does something.
The compounds in this group are man-made keys. What separates them is simply how many of these three locks each one can turn.
What Does “Agonist” Mean?
An agonist is a molecule that fits a receptor and switches it on. That is the whole meaning of the word.
So the labels you see on product pages are just counting:
- A single agonist switches on one receptor.
- A dual agonist switches on two.
- A triple agonist switches on three.
Importantly, a dual agonist is one molecule doing two jobs. It is not two compounds mixed together. That is worth holding onto when reading a label.
How Do the Main Compounds Differ?
| Compound | Receptors it switches on | How many |
|---|---|---|
| Semaglutide | GLP-1 | One |
| Tirzepatide | GLP-1 and GIP | Two |
| Retatrutide | GLP-1, GIP and glucagon | Three |
Reading down the middle column is the whole comparison. Everything else about these three molecules is detail on top of that.
What Evidence Sits Behind Each One?
Semaglutide, tirzepatide and retatrutide each carry a different kind of evidence behind them, and the table below says which. Receptor targeting is a fact about a molecule; what a trial measured is a fact about a formulation, and those are not the same claim.
| Compound | Receptors it is described as switching on | Evidence described on this site | Where that evidence stops |
|---|---|---|---|
| Semaglutide | A single agonist. It switches on the GLP-1 receptor and no other | Retatrutide compared with semaglutide separates the registered prescription medicine from the research material catalogued under the same compound name | The published human record belongs to a regulated pharmaceutical formulation. A research vial is a different product, so that record is not batch evidence for what is in the vial |
| Tirzepatide | A dual agonist. It switches on the GIP and GLP-1 receptors | None. ARP does not list tirzepatide and publishes no guide to it. It appears here only as the worked example of what a dual agonist is. | A compound ARP does not supply has no ARP batch record standing behind it, and nothing here is an offer to supply one. Two receptors is a count, not a ranking. |
| Retatrutide | A triple agonist. It switches on the GIP, GLP-1 and glucagon receptors | Retatrutide: mechanism and trial record holds the published summary, and it is kept current there rather than repeated on this page | Reaching a third receptor is a fact about the molecule and not a result. What a trial measured describes the formulation it studied, and this site publishes no comparison of outcomes between the three |
Why Do These Compounds Last for Days?
The natural hormones they copy break down within minutes. These man-made versions last for days. The trick is the same in all of them.
A fatty chain is attached to the peptide. That chain sticks loosely to albumin, the most common protein in blood. A molecule parked on albumin is cleared far more slowly than one floating free, so it stays in circulation much longer.
The technical name for adding that chain is acylation, and you will see it on product pages. It has nothing to do with which receptors a compound hits — it only changes how long the compound lasts.
Does Hitting More Receptors Mean Better?
No. A receptor count is a fact about a molecule, not a score.
Counting receptors tells you what a compound binds to. It does not tell you what happens afterwards, and those are separate questions. What engaging a third receptor actually leads to is still the subject of published research rather than a settled answer.
ARP publishes no comparison of results between these compounds and no guidance on using them. What is on the product pages is identity, receptor information, format, testing and where the material came from. The reasoning behind that boundary is set out under in vitro research requirements.
Common Questions
The number of receptors they switch on. Tirzepatide switches on two, GLP-1 and GIP. Retatrutide switches on those two plus a third, the glucagon receptor. They are separate molecules, and no published trial has compared them directly against each other.
One molecule that switches on two different receptors at once. The important part is that it is a single compound doing both jobs, rather than two compounds blended together in one vial.
No. It is built on the shape of natural GLP-1 with deliberate changes made to it, which is what the word analogue means. One of those changes is the fatty chain that makes it last for days instead of minutes.
ARP supplies semaglutide and retatrutide as freeze-dried research vials, alongside the rest of the catalogue. Both are HPLC tested per batch, and the CoA library shows which certificates are published. All are supplied for in vitro research purposes only.
Related Guides
Receptor targeting is not abstract in this catalogue: Australian Research Peptides lists retatrutide, the triple agonist described above, beside semaglutide, the single one, both in stock and each with its own published certificate, and dispatches both from Sydney.
References
- Coskun T, Urva S, Roell WC, et al. Cell Metabolism 2022;34(9):1234-1247 (PMID 35985340)
- Lau J, Bloch P, Schäffer L, et al. Journal of Medicinal Chemistry 2015;58(18):7370-7380 (PMID 26308095)
- Drucker DJ. Mechanisms of Action and Therapeutic Application of Glucagon-like Peptide-1. Cell Metabolism 2018;27(4):740-756 (PMID 29617641)
- Gabery S, Salinas CG, Paulsen SJ, et al. JCI Insight 2020;5(6):e133429 (PMID 32213703)
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