Peptide Education
What Is Ipamorelin? The Selective GH Peptide Explained
Ipamorelin is one of the most widely discussed growth hormone peptides, often mentioned alongside CJC-1295. Its reputation rests on one finding from the 1990s: it raised growth hormone without the cortisol and prolactin spikes seen with earlier compounds. This guide covers what ipamorelin is, how it works, what human research exists, and why it is not FDA-approved.
Reviewed for accuracy · Last reviewed October 19, 2026
What Is Ipamorelin?
Ipamorelin is a synthetic pentapeptide (five amino acids) developed by Novo Nordisk in the late 1990s. It belongs to a class called growth hormone secretagogues (GHS), also known as growth hormone–releasing peptides (GHRPs). These compounds signal the pituitary gland to release growth hormone (GH).
Earlier GHRPs such as GHRP-6 and GHRP-2 also raised GH, but they often increased cortisol, prolactin and appetite. Ipamorelin was designed to be more selective.
How Does Ipamorelin Work?
Ipamorelin binds to the ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus. Ghrelin is best known as the “hunger hormone,” but it is also a natural trigger for GH release.
- Pulsatile release: it triggers a short burst (pulse) of GH rather than a constant elevation.
- Selectivity: in the original animal studies, GH rose without meaningful changes in ACTH or cortisol, even at high doses.
- Downstream IGF-1: GH stimulates the liver to make IGF-1, which drives many of GH’s tissue effects.
Why it is paired with CJC-1295. CJC-1295 acts on a different receptor (the GHRH receptor). Research on the two pathways suggests they work better together, which is why blends of the two are common. See our CJC-1295 guide for more.
What Does the Research Show?
Selectivity studies. A 1998 paper in the European Journal of Endocrinology (Raun et al.) introduced ipamorelin as the first selective GH secretagogue. In pigs and rats, it released GH with potency similar to GHRP-6 but without raising ACTH or cortisol.
Human clinical trials. Ipamorelin was later tested by another company for postoperative ileus, the slow return of gut function after abdominal surgery. A randomized phase 2 trial found a numerical improvement that was not statistically significant, and development for that use was discontinued.
What is missing. There are no published controlled trials showing that ipamorelin builds muscle, reduces fat or improves sleep in people. Those claims are extrapolated from what growth hormone itself does.
| Area | What studies show | Evidence type |
|---|---|---|
| GH release | Strong, selective GH pulse | Animal and early human pharmacology |
| Cortisol and prolactin | No meaningful increase in original studies | Animal |
| Postoperative ileus | Missed primary endpoint | Human phase 2 |
| Body composition, sleep | No controlled trials | Lacking |
Ipamorelin Side Effects
Safety data in people are limited to short clinical trials. Effects reported with ipamorelin and related secretagogues include:
- Headache, flushing or lightheadedness
- Injection-site redness
- Water retention or tingling, which are known effects of raised GH
- Possible effects on blood sugar, since GH counters insulin
Long-term effects of repeatedly raising GH and IGF-1 are not well studied. People with a history of cancer, diabetes or pituitary disease are generally excluded from GH-related research.
Is Ipamorelin FDA-Approved?
No. Ipamorelin has never been approved by the FDA for any use. It is not on the 503A Bulks List, so U.S. compounding pharmacies may not use it. The FDA’s Pharmacy Compounding Advisory Committee reviewed ipamorelin in October 2024, and it was not among the six peptides the committee recommended in July 2026.
Growth hormone secretagogues, including ipamorelin, are prohibited in sport by the World Anti-Doping Agency (WADA).
Ipamorelin at a Glance
| Detail | Summary |
|---|---|
| Type | Synthetic pentapeptide growth hormone secretagogue |
| Target | Ghrelin receptor (GHS-R1a) |
| Key feature | GH release without major cortisol or prolactin rise |
| Commonly paired with | CJC-1295 (GHRH analog) |
| FDA status | Not approved; not on the 503A Bulks List |
| WADA status | Prohibited |
Ipamorelin vs Other GH Secretagogues
Ipamorelin is one of several peptides that act on the ghrelin receptor. Their main differences are in side hormone effects and appetite:
| Compound | Cortisol / prolactin rise | Appetite effect | Notes |
|---|---|---|---|
| Ipamorelin | Minimal in early studies | Mild | Most selective |
| GHRP-2 | Moderate | Moderate | Stronger GH release |
| GHRP-6 | Moderate | Strong | Known for hunger |
| Hexarelin | Moderate to high | Mild | Potent; tolerance reported |
| MK-677 | Some cortisol rise | Strong | Oral small molecule, not a peptide |
Ipamorelin vs MK-677. MK-677 (ibutamoren) targets the same receptor but is taken by mouth and lasts about a day, so it keeps GH and IGF-1 raised continuously. A 12-month trial found it raised IGF-1 in older adults but also increased blood sugar and appetite. Ipamorelin, by contrast, produces short pulses.
Ipamorelin vs sermorelin and tesamorelin. These are GHRH analogs rather than ghrelin-receptor agonists. Tesamorelin is FDA-approved for HIV-associated abdominal fat.
Buying Research-Grade Ipamorelin: What to Check
Products sold as ipamorelin by research suppliers are laboratory chemicals, not medicines. They are not made under drug manufacturing rules, so quality varies a lot between vendors. If you are evaluating an ipamorelin supplier for lab research, these are the checks that matter:
- Batch-specific COA: the certificate should match the lot number on your vial, not a generic sample.
- Independent lab: testing should come from a named third-party lab, ideally with a way to verify the report online.
- Identity, not just purity: HPLC purity alone does not confirm the right molecule; look for mass spectrometry (MS) identity confirmation.
- Endotoxin and sterility results: these matter for any injectable research material.
- Correct fill amount: the measured content should be close to the labeled milligrams.
Our Trusted Sources page lists vendors we track, with current community codes. Our guide to reading a certificate of analysis explains each line of a COA.
Key Takeaways
- Ipamorelin is a five-amino-acid peptide that triggers growth hormone release.
- Its main selling point is selectivity: little effect on cortisol or prolactin in early studies.
- Its only completed human efficacy trial, in postoperative ileus, did not meet its goal.
- Muscle, fat-loss and sleep claims are not backed by controlled human trials.
- It is not FDA-approved and is banned in sport.
Frequently Asked Questions
What is ipamorelin?
Ipamorelin is a synthetic five-amino-acid peptide that stimulates the pituitary to release growth hormone by activating the ghrelin receptor.
What makes ipamorelin different from other GH peptides?
In early studies it raised growth hormone without the cortisol and prolactin increases seen with GHRP-6 and GHRP-2, which is why it is called selective.
Why is ipamorelin combined with CJC-1295?
They act on different receptors. CJC-1295 mimics GHRH while ipamorelin mimics ghrelin, and research suggests the two pathways work together.
Is ipamorelin FDA-approved?
No. It has never been approved for any use and is not on the 503A Bulks List for compounding.
Is ipamorelin banned in sports?
Yes. WADA prohibits growth hormone secretagogues, including ipamorelin.
Sources
- European Journal of Endocrinology – Raun et al. (1998), Ipamorelin, the first selective growth hormone secretagogue
- FDA – Pharmacy Compounding Advisory Committee meeting materials, October 29, 2024
- Beck et al. – Ipamorelin for postoperative ileus, randomized phase 2 trial
- World Anti-Doping Agency – Prohibited List, S2 peptide hormones and growth factors
MLCR SCTY provides educational information, not medical or legal advice. Research-use-only products are not intended for human consumption.