Educational reference, not medical advice. This page summarizes information from published research and regulatory filings for educational purposes. It is not a recommendation to use any compound and should not replace guidance from a licensed healthcare provider. Most peptides discussed here are not approved for the uses described.
What it is
Ipamorelin is a synthetic pentapeptide — five amino acids, sequence Aib-His-D-2-Nal-D-Phe-Lys-NH₂ — that activates the growth hormone secretagogue receptor (GHSR-1a), the same receptor that binds the endogenous hormone ghrelin. It was designed at Novo Nordisk as a more selective alternative to earlier growth hormone-releasing peptides such as GHRP-6 and GHRP-2, which also raise cortisol and prolactin alongside growth hormone.
History
Ipamorelin was first described by Kirsten Raun and colleagues at Novo Nordisk in a 1998 paper in the European Journal of Endocrinology, where they reported it as "the first selective growth hormone secretagogue." The Raun paper demonstrated that, unlike GHRP-6 and GHRP-2, ipamorelin produced a GH pulse comparable to native GHRH without raising ACTH, cortisol, FSH, LH, prolactin, or TSH above background.
Novo Nordisk (and later Helsinn Therapeutics, which licensed the compound) advanced ipamorelin into Phase II clinical trials for postoperative ileus — the temporary intestinal paralysis that follows abdominal surgery — based on the gut-motility effects of ghrelin-receptor agonism. The Phase II program for that indication was completed in 2006 and ultimately reported negative; the published Phase II results (Beck et al., 2014) showed no significant benefit over placebo on the primary endpoint. Development was discontinued and ipamorelin has not been advanced by any subsequent sponsor.
Regulatory status
Ipamorelin has no approved medical use in any major jurisdiction. The FDA has not approved it, and it is not on the 503A bulk substances list — compounding pharmacies in the United States are not permitted to prepare it for patients. The European Medicines Agency has not authorized it.
The World Anti-Doping Agency lists ipamorelin under class S2 of the Prohibited List (peptide hormones, growth factors, related substances, and mimetics) — banned in and out of competition.
Mechanism
Published mechanism papers describe ipamorelin as a selective agonist of the ghrelin/GHSR-1a receptor on anterior pituitary somatotrophs. Receptor activation stimulates phospholipase C and inositol triphosphate signaling, raising intracellular calcium and triggering growth hormone release.
The selectivity that distinguishes ipamorelin from GHRP-6 and GHRP-2 is attributed to its weaker activation of receptors on hypothalamic neurons that drive ACTH and prolactin release. The clinical relevance of this selectivity is that ipamorelin produces a GH pulse without the cortisol or prolactin co-elevation seen with earlier-generation GHRPs.
Because ipamorelin acts on a separate pathway from GHRH, it is commonly paired with GHRH analogs (sermorelin, CJC-1295) in observational use; the two pathways are synergistic and produce a larger GH pulse together than either alone.
Half-life and dosing intervals
The published plasma half-life of ipamorelin is approximately 2 hours after subcutaneous injection — longer than sermorelin or Mod GRF 1-29 but far shorter than the DAC-modified analogs.
In the Beck et al. Phase II trial for postoperative ileus, ipamorelin was administered intravenously at 0.03 mg/kg twice daily for up to seven days. In Raun's preclinical work, the doses that produced reproducible GH pulses in rats and swine were in the range of 1 to 100 mcg/kg subcutaneously.
There is no established human subcutaneous dose for any other indication. In observational use the peptide is typically administered at 100 to 300 mcg per dose, once to three times daily, with the timing chosen to align with reported GH pulses. These patterns are extrapolations from preclinical work, not from a controlled clinical trial.
Reconstitution example
Ipamorelin is sold lyophilized in 2 mg or 5 mg vials. A 2 mg vial reconstituted with 2 mL of bacteriostatic water yields 1 mg/mL — on a 1 mL U-100 insulin syringe, 10 units (0.1 mL) contains 100 mcg.
A 5 mg vial reconstituted with 2 mL of bacteriostatic water yields 2.5 mg/mL — the same 10-unit mark contains 250 mcg. Vial's calculator handles the unit-to-microgram conversion automatically.
What to know
- Limited human data. The only published Phase II trial (postoperative ileus) was negative on its primary endpoint. There are no published controlled studies on long-term subcutaneous use.
- Not approved. No regulator has authorized ipamorelin for therapeutic use, and compounding for patients is not permitted in the United States.
- WADA banned. Use is prohibited in competitive sport.
- Selectivity. Ipamorelin is the most receptor-selective of the ghrelin-receptor agonists in this class, with minimal effect on cortisol and prolactin in published work.
- Reported side effects in observational use are typically mild — headaches, injection-site reactions, and transient hunger (consistent with the ghrelin-receptor activity). Hunger tends to be less pronounced than with GHRP-6.
- Storage. Lyophilized vials are best stored refrigerated. Once reconstituted, refrigerate and use within 4 weeks per typical supplier stability data.
Sources
- 1.Raun K et al. (1998). Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology.
- 2.Beck DE et al. (2014). Ipamorelin for the management of postoperative ileus in patients undergoing partial bowel resection: a Phase II clinical trial. Diseases of the Colon and Rectum.
- 3.Sigalos JT, Pastuszak AW (2018). The Safety and Efficacy of Growth Hormone Secretagogues. Sexual Medicine Reviews.
- 4.World Anti-Doping Agency — Prohibited List (S2).