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Ipamorelin
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Research

What the Studies Found

Keep in mind: Most ipamorelin research was done in rats. The human evidence consists of one study in healthy men and one published trial in surgical patients, which did not meet its main goal.

Around fifty papers in the PubMed database mention ipamorelin. The core findings come from a few groups and fall into four areas: pituitary effects, bone and muscle, body fat and metabolism, and the gut.

Pituitary Effects

  • Discovery paper (Eur J Endocrinol, 1998): in rat pituitary cells, ipamorelin released growth hormone about as potently as GHRP-6. In pigs it did not raise ACTH or cortisol beyond levels seen with GHRH.
  • Somatotroph cells (Histol Histopathol, 2002): after 21 days of treatment in young female rats, pituitary cells showed more secretory granules and a changed response to later stimulation.

Bone and Muscle in Rats

  • Bone length (Growth Horm IGF Res, 1999): over 15 days, the tibia grew faster in a dose-dependent way, from 42 to as much as 52 micrometres per day, and body weight rose. Total IGF-I did not change.
  • Bone mineral (J Endocrinol, 2000): twelve weeks of continuous delivery increased bone mineral content, but because the bones grew larger, not denser.
  • Steroid-induced loss (Growth Horm IGF Res, 1999 and 2001): in rats given methylprednisolone, ipamorelin reduced weight loss, raised IGF-I and, over three months, preserved calf muscle strength and periosteal bone formation.
  • Protein breakdown (Growth Horm IGF Res, 2009): in prednisolone-treated rats it reduced nitrogen loss, though less effectively than growth hormone itself.

Body Fat and Metabolism

  • Fat gain (Biochem Biophys Res Commun, 2001): in mice, ipamorelin increased body fat even in animals lacking growth hormone, along with higher food intake and leptin. The authors linked this to the ghrelin pathway rather than growth hormone.
  • Insulin (Neuro Endocrinol Lett, 2004): in isolated pancreas tissue from normal and diabetic rats, ipamorelin increased insulin release.

Studies in People

  • Pharmacokinetics (Pharm Res, 1999): in healthy men studied at five infusion rates, blood levels rose in proportion to dose and the half-life was about two hours. Each infusion produced one growth hormone episode that peaked after roughly 40 minutes.
  • Postoperative ileus (Int J Colorectal Dis, 2014): in 114 patients analysed after bowel surgery, the median time to tolerating a solid meal was 25.3 hours with ipamorelin and 32.6 hours with placebo, a difference that was not statistically significant. Adverse events were frequent in both groups, at 87.5% and 94.8%, and the drug was described as well tolerated.

Other Animal Work

In rats after abdominal surgery, repeated intravenous doses increased stool output and food intake (2009). In ferrets given the chemotherapy drug cisplatin, ipamorelin reduced weight loss late in the treatment period by about a quarter but did not reduce vomiting (2024).

Doping Analysis

Cologne's anti-doping laboratory mapped how ipamorelin and related peptides break down in the body in 2012. Black-market products examined by German and Norwegian laboratories, and powders seized by Danish customs, contained a modified form with an extra glycine at the start, so testing methods had to be updated.

What Is Missing

  • There are no published long-term studies in humans.
  • Results of the second, larger Phase 2 trial have not been posted.
  • Much of the early work was carried out by the developing company or its partners.
  • A 2026 review in Sports Medicine concluded that rigorous human safety data for unapproved peptides such as ipamorelin are scarce.

Summary

Ipamorelin reliably triggers a brief growth hormone release, and rat studies point to effects on bone, muscle and fat. The one published patient trial was negative, and no study has shown a clinical benefit in people.

References

  1. Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139:552-561. PMID 9849822
  2. Johansen PB, et al. Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption. Xenobiotica. 1998;28:1083-1092. PMID 9879640
  3. Gobburu JV, et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res. 1999;16:1412-1416. PMID 10496658
  4. Johansen PB, et al. Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Growth Horm IGF Res. 1999;9:106-113. PMID 10373343
  5. Malmlöf K, et al. Methylprednisolone does not inhibit the release of growth hormone after intravenous injection of a novel growth hormone secretagogue in rats. Growth Horm IGF Res. 1999;9:445-450. PMID 10629165
  6. Svensson J, et al. The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats. J Endocrinol. 2000;165:569-577. PMID 10828840
  7. Lall S, et al. Growth hormone (GH)-independent stimulation of adiposity by GH secretagogues. Biochem Biophys Res Commun. 2001;280:132-138. PMID 11162489
  8. Andersen NB, et al. The growth hormone secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats. Growth Horm IGF Res. 2001;11:266-272. PMID 11735244
  9. Jiménez-Reina L, et al. Influence of chronic treatment with the growth hormone secretagogue Ipamorelin, in young female rats: somatotroph response in vitro. Histol Histopathol. 2002;17:707-714. PMID 12168778
  10. Adeghate E, Ponery AS. Mechanism of ipamorelin-evoked insulin release from the pancreas of normal and diabetic rats. Neuro Endocrinol Lett. 2004;25:403-406. PMID 15665799
  11. Aagaard NK, et al. Growth hormone and growth hormone secretagogue effects on nitrogen balance and urea synthesis in steroid treated rats. Growth Horm IGF Res. 2009;19:426-431. PMID 19231263
  12. Venkova K, et al. Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus. J Pharmacol Exp Ther. 2009;329:1110-1116. PMID 19289567
  13. Thomas A, et al. Metabolism of growth hormone releasing peptides. Anal Chem. 2012;84:10252-10259. PMID 23101768
  14. Beck DE, et al. 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. 2014;29:1527-1534. PMID 25331030
  15. Krug O, et al. Analysis of new growth promoting black market products. Growth Horm IGF Res. 2018;41:1-6. PMID 29864719
  16. Gajda PM, et al. Glycine-modified growth hormone secretagogues identified in seized doping material. Drug Test Anal. 2019;11:350-354. PMID 30136411
  17. Lu Z, et al. The growth hormone secretagogue receptor 1a agonists, anamorelin and ipamorelin, inhibit cisplatin-induced weight loss in ferrets. Physiol Behav. 2024;284:114644. PMID 39043357
  18. Mendias CL, Awan TM. Safety and efficacy of approved and unapproved peptide therapies for musculoskeletal injuries and athletic performance. Sports Med. 2026;56:1921-1935. PMID 41966639
  19. Helsinn Therapeutics (U.S.). Safety and efficacy of ipamorelin for management of post-operative ileus. ClinicalTrials.gov NCT00672074.
  20. Helsinn Therapeutics (U.S.). Safety and efficacy of ipamorelin compared to placebo for the recovery of gastrointestinal function. ClinicalTrials.gov NCT01280344.