Tesamorelin vs Ipamorelin: two routes to GH release
Tesamorelin vs ipamorelin is a common growth hormone research comparison. Both trigger GH release, but through different receptors. Tesamorelin is a 44-amino-acid GHRH analog. Ipamorelin is a 5-amino-acid peptide that acts on the ghrelin receptor (GHS-R1a). Tesamorelin is the active ingredient of an FDA-approved medicine; ipamorelin is not approved. Both are sold here, separately and as a blend, for laboratory research use only.
Side-by-side comparison
| Tesamorelin | Ipamorelin | |
|---|---|---|
| Class | GHRH analog | Ghrelin-receptor agonist (GHRP) |
| Receptor | GHRH receptor | GHS-R1a |
| Length | 44 amino acids | 5 amino acids |
| Key research | Randomised trials in HIV-associated abdominal fat | Animal studies of selective GH release |
| Regulatory status | Active ingredient of an FDA-approved medicine | Not approved |
Tesamorelin vs ipamorelin at a glance
Both peptides make the pituitary release growth hormone (GH). They do it through different receptors.
Tesamorelin copies GHRH, the hormone that tells the pituitary to release GH. Ipamorelin copies ghrelin, a second signal that also triggers GH release.
So the end result looks similar. The starting point is not.
Two receptors, one hormone output
Tesamorelin binds the GHRH receptor. Ipamorelin binds the ghrelin receptor, GHS-R1a.
Both receptors sit on the same pituitary cells, called somatotrophs. Each one switches on its own signalling route inside the cell.
A shared rise in GH does not make the two compounds interchangeable. It does explain why researchers often study them together.
Structure and stability
Tesamorelin is 44 amino acids long. It matches natural GHRH(1-44), plus a trans-3-hexenoyl group at one end. That group slows breakdown by the enzyme DPP-4.
Ipamorelin has only five residues: Aib-His-D-2-Nal-D-Phe-Lys-NH2. Several are non-natural building blocks that resist enzyme cleavage.
Size matters in the lab. It affects synthesis cost, solubility, handling and behaviour in a model system.
What the studies found
Tesamorelin has randomised human trials. In a 26-week trial, it reduced visceral (deep belly) fat versus placebo in adults with HIV-associated abdominal fat (Falutz et al., 2007).
Follow-up work reported longer-term safety and what happened after treatment stopped (Falutz et al., 2008). A later trial also tracked liver fat (Stanley et al., 2014).
Ipamorelin's key paper is an animal study. It called ipamorelin the first selective GH secretagogue (Raun et al., 1998). It released GH without the large ACTH and cortisol rises seen with some older GHRPs.
- Tesamorelin: randomised human trials in one defined patient group.
- Ipamorelin: animal studies of selectivity, plus early-phase work.
- The two evidence bases differ in strength and type.
Selectivity and the cortisol question
Ipamorelin's main claim is selectivity. In animal work, it raised GH without markedly raising ACTH, cortisol or prolactin.
That claim compares ipamorelin with older ghrelin mimetics such as GHRP-6. It is not really a contrast with tesamorelin. The GHRH receptor sits mainly on GH-producing cells, so GHRH analogs do not drive those other hormones either.
Why they are studied as a blend
Hitting both receptors at once is a logical idea at the receptor level. It is still a hypothesis for the commercial blend.
No controlled study of the tesamorelin + ipamorelin combination is cited here. The ratio in a blend vial is a product specification, not a published optimum.
Choosing between them in a study design
Pick tesamorelin if your question is about the GHRH pathway, or if you want to match the published clinical work.
Pick ipamorelin if your question is about ghrelin-receptor signalling or secretagogue selectivity.
Either way, GH comes out in pulses. Repeated sampling or an integrated measure tells you more than a single timepoint. IGF-1 is often used as a downstream marker.
Frequently asked questions
What is the main difference between tesamorelin and ipamorelin?
Tesamorelin acts on the GHRH receptor; ipamorelin acts on the ghrelin receptor GHS-R1a. They are structurally unrelated.
Which is larger?
Tesamorelin is a 44-amino-acid GHRH analog; ipamorelin is a five-residue peptide.
Do they both raise IGF-1?
Both act by stimulating the pituitary's own GH release, and GH in turn drives IGF-1. The published magnitude and duration data differ and are not directly comparable across those study designs.
Is one more selective than the other?
Ipamorelin's selectivity claim is against earlier ghrelin mimetics such as GHRP-6, which raised ACTH and cortisol. Tesamorelin acts on a receptor restricted to somatotrophs, so the comparison is not like-for-like.
Is tesamorelin or ipamorelin more studied in humans?
Tesamorelin has randomised human trials in HIV-associated abdominal fat; ipamorelin's published data are mostly early-phase and animal studies. See our research peptides guide research peptides guide for how to compare suppliers and read test documents.
Which one is approved?
Tesamorelin is the active ingredient of an FDA-approved medicine for one specific indication. Ipamorelin is not approved.
Why are they sold as a blend?
Because they act on separate receptors, GHRH analogs and ghrelin mimetics are often studied together. The blend is supplied for research only.
Product pages: Tesamorelin · Ipamorelin · Tesamorelin + Ipamorelin blend
Is there a study of the tesamorelin + ipamorelin blend?
No controlled study of the combined formulation is cited here. The pairing rests on component evidence and a receptor-level rationale.
Does the blend ratio come from research?
No. The ratio in a blend vial is a product specification, not a published optimised ratio.
How should GH release be measured in this research?
GH is released in pulses, so serial sampling or an integrated measure is more informative than a single timepoint; IGF-1 is commonly used as a downstream proxy.
How should both be stored?
Keep lyophilised vials cold, dry and away from light; refrigerate reconstituted solutions and avoid repeated freeze-thaw cycles.
Can I buy tesamorelin and ipamorelin separately?
Yes. Both are sold individually and as a blend, for laboratory research only. See our research peptides guide research peptides guide for how to compare suppliers and read test documents.
Product pages: Tesamorelin · Ipamorelin · Tesamorelin + Ipamorelin blend
Is this product for human use?
No. PeptidesDirect sells this compound for laboratory research only. It is not a drug, food or cosmetic and is not for human or veterinary use. This page summarises published research and is not dosing or medical guidance.
Shop the compounds covered in these FAQs: Tesamorelin · Ipamorelin · Tesamorelin + Ipamorelin blend
References
- Falutz J, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. 2007. PubMed 18057338
- Falutz J, et al. Long-term safety and effects of tesamorelin, a growth hormone-releasing factor analogue, in HIV patients with abdominal fat accumulation. AIDS. 2008. PubMed 18690162
- Stanley TL, et al. Effect of tesamorelin on visceral fat and liver fat in HIV-infected patients with abdominal fat accumulation: a randomized clinical trial. JAMA. 2014. PubMed 25038357
- Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998. PubMed 9849822
Research compounds
Related guides
Research Use Only. Not for human or veterinary use. Not dosing or medical guidance.
