Compare
Ipamorelin vs sermorelin
Sermorelin is a GHRH (1-29) fragment acting at the GHRH receptor; ipamorelin acts at GHSR-1a. Their targets and human evidence compared.
By the Ipamorelin Research editorial team · Last reviewed · Scientific review: pending
Short answer
Sermorelin is the 1-29 fragment of growth hormone-releasing hormone and acts at the GHRH receptor. Ipamorelin is a five-residue synthetic peptide acting at GHSR-1a, the ghrelin receptor. They stimulate growth hormone release through two separate systems. No head-to-head human trial of the two exists, and comparisons between them rest on mechanism rather than on measured outcomes.
| Field | Ipamorelin | Sermorelin |
|---|---|---|
| Classification | Synthetic pentapeptide growth hormone secretagogue | GHRH (1-29) fragment |
| Receptor target | GHSR-1a | GHRH receptor |
| Molecular formula | C38H49N9O5 | C149H246N44O42S |
| Molecular weight | 711.9 | 3357.9 |
| Size | 5 residues, C-terminal amide; three non-standard residues | 29 residues |
| Human clinical evidence | 1 randomised trial (null on efficacy); 1 dose-escalation PD study; 1 trial of 320 never reported | Not assessed here; the review in this database reports class-wide data gaps |
| Regulatory status | Not approved; FDA Category 2; advisory committee voted against 503A listing | No current Drugs@FDA match returned |
The cleanest example of the two-receptor distinction
Sermorelin is simply the shortest active fragment of the body's own growth hormone-releasing hormone, so it works the way GHRH works, at the GHRH receptor. Ipamorelin is a synthetic molecule bearing no resemblance to GHRH — three of its five residues do not occur in ordinary proteins — and it works at GHSR-1a, the receptor for ghrelin. The antagonist profiling in the original ipamorelin characterisation established that distinction directly: the GH-releasing effect was blocked by GHRP antagonists and not by a GHRH antagonist[Raun 1998].
In practice this means the two compounds are not substitutes for each other in any mechanistic sense. They are different inputs to the same pituitary output. The full ipamorelin pathway is on the mechanism page.
Size and chemistry
Sermorelin is a 29-residue peptide at about 3,358 g/mol, nearly five times the mass of ipamorelin at 711.9 g/mol [PubChem]. Being a natural GHRH fragment, sermorelin is built entirely from standard amino acids; ipamorelin's unnatural residues and C-terminal amide are what give it a measured two-hour half-life in humans [Gobburu 1999].
What is established for ipamorelin
One randomised controlled trial, in 117 postoperative patients, with no significant difference from placebo on its efficacy endpoints [Beck 2014]. One dose-escalation study in 40 healthy men, measuring a single growth hormone pulse [Gobburu 1999]. One further trial of 320 patients that completed in 2014 and has never reported [NCT01280344]. There is no approved application for ipamorelin[openFDA], and no validated dose for any purpose.
On sermorelin's regulatory status
A Drugs@FDA query by generic name returns no current match for sermorelin[openFDA]. openFDA's coverage of discontinued products is incomplete, so that result is reported here as exactly what the query returned and should not be read as a statement about sermorelin's historical approval status, which this site has not verified. Ipamorelin's own regulatory record is documented in full.
References
- Raun K, Hansen BS, Johansen NL et al. (1998). Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. PubMed 9849822 · doi:10.1530/eje.0.1390552[Animal, grade C]
- Gobburu JV, Agersø H, Jusko WJ et al. (1999). Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res. PubMed 10496658 · doi:10.1023/a:1018955126402[Human, grade B]
- Beck DE, Sweeney WB, McCarter MD et al. (2014). Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis. PubMed 25331030 · doi:10.1007/s00384-014-2030-8[Human, grade A]
- Sinha DK, Balasubramanian A, Tatem AJ et al. (2020). Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Transl Androl Urol. PubMed 32257855 · doi:10.21037/tau.2019.11.30[Review, grade R]
- PubChem, National Library of Medicine. Ipamorelin (CID 9831659). Source[retrieved 2026-11-11]
- U.S. Food and Drug Administration, openFDA. openFDA Drugs@FDA and NDC directory queries for ipamorelin. Source[retrieved 2026-11-11]
- ClinicalTrials.gov, U.S. National Library of Medicine (2011-04). Phase II Double-Blind Placebo-Controlled Dose Finding Study to Evaluate Safety/Efficacy of Ipamorelin Compared to Placebo for Recovery of Gastrointestinal Function Following Bowel Resection (NCT01280344). Source[retrieved 2026-11-11]