Educational reference. Research use only.
Ipamorelin: Mechanism, Research, and Regulatory Status
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue, sequence Aib-His-D-2Nal-D-Phe-Lys-NH2, CAS 170851-70-4, molecular weight 711.85 Da, that acts at the ghrelin receptor. Ipamorelin has been studied in 1 published human trial, a 2014 Phase 2 trial; the rest of the evidence is preclinical. Ipamorelin is not approved for human use.
Last reviewed 2026-09-29
What is Ipamorelin?
Ipamorelin key facts
Ipamorelin is a synthetic pentapeptide with the sequence Aib-His-D-2Nal-D-Phe-Lys-NH2, CAS number 170851-70-4 and a molecular weight of 711.85 Da. Raun and colleagues described ipamorelin in the European Journal of Endocrinology in 1998 as the first selective growth hormone secretagogue. Ipamorelin acts as a partial agonist at the ghrelin receptor GHS-R1a on pituitary somatotrophs, prompting pulsatile growth hormone release, with minimal reported effect on ACTH, cortisol, aldosterone or prolactin. Johansen and colleagues reported in Growth Hormone & IGF Research in 1999 that ipamorelin increased longitudinal bone growth in adult female rats, and Andersen and colleagues reported in 2001 that ipamorelin counteracted a glucocorticoid-induced decrease in bone formation in rats. The one published human trial, a Phase 2 study in postoperative ileus (Beck and colleagues, International Journal of Colorectal Disease, 2014, n=114), found ipamorelin well tolerated but not significantly different from placebo on its efficacy endpoints. Ipamorelin is not approved by any regulator, is prohibited by WADA under S2, and is supplied for research use only.
How does Ipamorelin work?
Ipamorelin is a selective growth hormone secretagogue pentapeptide, a five-amino-acid chain that prompts the pituitary to release its own growth hormone. It acts as a partial agonist at the ghrelin receptor (GHS-R1a), stimulating pulsatile GH release from pituitary somatotrophs. Unlike older GH secretagogues, ipamorelin is highly selective, with minimal effects on ACTH, cortisol, aldosterone, or prolactin.
What has research on Ipamorelin found?
What published peer-reviewed research and preclinical studies have established about Ipamorelin:
- 01Selective growth hormone secretagogue pentapeptide acting on the ghrelin/GHS receptor (GHS-R1a)
- 02Preclinical studies demonstrate dose-dependent GH release with minimal effects on cortisol and prolactin compared to other GH secretagogues
- 03Animal models suggest favorable selectivity profile with lower impact on ACTH and aldosterone release
- 04Investigated clinically for post-operative ileus recovery in a Phase 2 proof-of-concept trial, which did not meet its efficacy endpoints (Beck 2014)
- 05Induced dose-dependent longitudinal bone growth in hypophysectomised rats, an effect abolished by GH-receptor blockade. That is evidence the skeletal signal runs through GH rather than a direct action on bone (Johansen 1999)
- 06Counteracted glucocorticoid-induced suppression of bone formation in adult rats, one of the few models where a secretagogue restored a drug-induced deficit rather than adding to a normal baseline (Andersen 2001)
- 07Acts on the same receptor as ghrelin but is a pentapeptide rather than a 28-residue acylated peptide, which is why its GH signal is pulsatile and short-lived rather than sustained
Which studies have examined Ipamorelin?
Ipamorelin for post-operative ileus (Phase 2 RCT)
Phase 2 RCT · 2014Well tolerated; no significant difference vs placebo on the key or secondary efficacy endpoints (median time to first tolerated meal 25.3 vs 32.6 h, p=0.15)
Frequently asked questions about Ipamorelin
Is ipamorelin selective for GH vs cortisol?+
Yes. Ipamorelin was specifically developed and characterized for its high GHS-R1a selectivity without stimulating ACTH or cortisol release, which distinguishes it from GHRP-2 and GHRP-6. This selectivity was confirmed in Phase 1 human data.
How does ipamorelin differ from CJC-1295?+
They act on entirely different receptors and are complementary rather than interchangeable. Ipamorelin is a ghrelin-receptor (GHS-R1a) agonist that triggers a discrete GH pulse from the pituitary. CJC-1295 is a GHRH analog acting on the GHRH receptor, raising the baseline from which those pulses occur. Because the two pathways are separate, combining them produces a larger response than either alone, which is why the blend exists as its own research entry.
What is the half-life of ipamorelin?+
Roughly two hours in published pharmacokinetic work, substantially shorter than CJC-1295 with DAC, which binds serum albumin and persists for days. The short half-life is the point rather than a limitation: it produces a pulse that approximates physiological GH release instead of a continuous elevation.
How does ipamorelin compare to GHRP-2 and GHRP-6?+
All three are ghrelin-receptor agonists, but the older GHRP-2 and GHRP-6 also stimulate ACTH, cortisol and prolactin, and GHRP-6 in particular produces marked appetite stimulation. Ipamorelin was designed specifically to keep the GH signal while dropping those off-target effects, and that selectivity is its defining characteristic in the literature.
Why did the postoperative ileus program not continue?+
The Phase 2 proof-of-concept study in bowel-resection patients found ipamorelin well tolerated but reported no significant difference from placebo on its key or secondary efficacy endpoints (Beck 2014), and the compound did not go on to approval. Ipamorelin has no approved indication in any jurisdiction.
Does the receptor desensitize with continued exposure?+
Sustained GHS-R1a agonism attenuates the GH response over time in animal models. This is one reason the short half-life, which yields discrete pulses rather than continuous receptor occupancy, is treated as a design feature in the published work.
What does the bone research actually show?+
Two rat studies are the substantive skeletal evidence. Johansen (1999) found dose-dependent longitudinal bone growth that disappeared when the GH receptor was blocked, showing the effect is GH-mediated rather than a direct action on bone. Andersen (2001) found ipamorelin counteracted glucocorticoid-induced suppression of bone formation. Both are animal models; neither has a human equivalent.
How should ipamorelin be stored?+
As a lyophilized powder, at -20°C, desiccated and protected from light. Repeated freeze-thaw cycles degrade peptide integrity and should be avoided.
References & sources
Every citation below was resolved against its primary source before publication. Each PMID was checked against its PubMed record and each DOI through doi.org. Follow any link to read the paper at the publisher rather than taking our summary on trust.
- [1]Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998. PMID: 9849822 DOI: 10.1530/eje.0.1390552
- [2]Beck DE, Sweeney WB, McCarter MD. Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. International Journal of Colorectal Disease. 2014. PMID: 25331030 DOI: 10.1007/s00384-014-2030-8
- [3]Johansen PB, Nowak J, Skjaerbaek C, et al. Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Growth Hormone & IGF Research. 1999. PMID: 10373343 DOI: 10.1054/ghir.1999.9998
- [4]Andersen NB, Malmlof K, Johansen PB, Andreassen TT. The growth hormone secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats. Growth Hormone & IGF Research. 2001. PMID: 11735244 DOI: 10.1054/ghir.2001.0239
Where this data comes from
- Citations & trial data: PubMed (NCBI, U.S. National Library of Medicine), Crossref and ClinicalTrials.gov.
- Chemical identity: PubChem and UniProt. Where sources conflicted, the disputed value is omitted rather than guessed.
- Regulatory status: U.S. FDA publications and, where applicable, the WADA Prohibited List. Compounding status changes often, so check FDA directly before relying on it.
- Purity, form and storage are handling and supplier conventions, not literature-derived values. Confirm against the lot-specific certificate of analysis. General handling is covered in the storage and stability guide.
Content last reviewed 2026-09-29. Compiled by Veridian Research from the primary literature. This page is an educational reference for laboratory researchers. It is not medical advice, and it describes no human use.
Is Ipamorelin approved for human use?
Ipamorelin is an investigational compound not approved for therapeutic use by the FDA or any regulatory agency. WADA classifies GH secretagogues as prohibited (S2). For research purposes only.
Research-use-only material
Specifications and certificate of analysis
Ipamorelin is stocked as a research reagent. Analytical documentation, covering identity, purity and the lot-specific certificate of analysis, is published in the certificate library.