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Ipamorelin

Ghrelin receptor agonist / growth hormone secretagogue

Also known as NNC 26-0161

A selective growth hormone secretagogue that reached phase II for postoperative ileus and was discontinued after missing its endpoints. A useful case study in what a negative trial looks like.

Guide updated Sep 2, 2026Literature checked Sep 2, 20262 curated studies25 literature recordsBaseline editorial
SequenceAib-His-D-2-Nal-D-Phe-Lys-NH2

Overview

In shortA small synthetic peptide that triggers growth hormone release, built to do that without the cortisol and prolactin bumps older versions caused. The most useful thing about it is that it was properly developed and then stopped: it entered mid-stage trials for a gut problem after surgery, missed its targets, and was dropped. That failure tells you more than silence, and it almost never comes up.

Ipamorelin is a synthetic pentapeptide ghrelin receptor agonist developed by Novo Nordisk. It was designed for selectivity: it releases growth hormone with substantially less effect on cortisol and prolactin than earlier secretagogues.

Its most instructive feature is that it was properly developed and then stopped. It went into phase II for postoperative ileus, did not meet its endpoints, and was discontinued. That failure is far more informative than the absence of evidence surrounding most unapproved compounds, and it is almost never mentioned in discussion of it.

Mechanism

In shortIt binds the same receptor as ghrelin, the hunger hormone, on the pituitary, which then releases your own growth hormone in pulses. Its selling point is what it does not do: it barely touches cortisol and prolactin at doses that release growth hormone. Hitting that receptor also gets the gut moving and raises appetite, which is what the trials were aiming at.

Ipamorelin binds the growth hormone secretagogue receptor (GHS-R1a), the ghrelin receptor, on pituitary somatotrophs and in the hypothalamus, producing a pulsatile release of endogenous growth hormone.

Its selling point mechanistically is selectivity. Minimal stimulation of ACTH, cortisol, and prolactin at GH-releasing doses, distinguishing it from earlier secretagogues. Ghrelin receptor agonism also produces prokinetic gastrointestinal effects and appetite stimulation, which is what the ileus programme was targeting.

Evidence

In shortEarly human work, and negative where it was actually tested. Studies confirmed it raises growth hormone with the selectivity claimed. The mid-stage trials in gut recovery after surgery missed their targets and development stopped. For body composition, recovery, sleep or ageing in healthy adults, the uses people actually discuss, there is no properly sized evidence at all.

Early clinical, and importantly negative where it was properly tested.

Human pharmacology studies established that it produces dose-dependent GH release with the claimed selectivity. Phase II trials in postoperative ileus did not meet primary endpoints, and development was discontinued.

For body composition, recovery, sleep, or ageing in healthy adults, the uses that dominate community discussion, there is no adequately powered human evidence at all. Reasoning from "it raises GH" to those outcomes is precisely the mechanism-is-not-a-result error.

Safety

In shortShort trial use was generally tolerated: headaches, injection site reactions, some effect on blood sugar. The concerns follow from keeping growth hormone raised over time: insulin resistance, fluid retention, joint pain, carpal tunnel symptoms, and the cell-growth implications of chronically raised IGF-1. Trial exposure was short and nobody has studied long-term use. Banned in sport.

Short-term human exposure in trials was generally well tolerated, with headache, injection site reactions, and transient effects on glucose reported.

The mechanistic concerns follow from sustained GH/IGF-1 elevation: insulin resistance, fluid retention, arthralgia, carpal tunnel symptoms, and the mitogenic implications of chronically raised IGF-1. Trial exposure was short; nobody has characterised long-term use.

No long-term safety data exists in healthy adults. Prohibited in sport under WADA's S2 category.

Regulatory status

In shortNever approved. Development stopped after mid-stage trials. Sold as a research chemical, banned in sport, and not made to medicine standards when bought outside a trial.

Never approved. Development discontinued after phase II. Sold as a research chemical, prohibited in sport, not manufactured to pharmaceutical standards when obtained outside a trial.

The literature

2 studies indexed. Findings and limitations get equal weight, on purpose.

Always check the primary source

Members area

The Ipamorelin literature needs an account

Everything above is free to read. What an account opens is the evidence underneath it: 2 studies with their limitations, and the regimen each trial actually reported.

  • Every study, with what it found and what it cannot show
  • The limitations, given the same weight as the findings
  • The dose each named trial administered, where recorded
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The wider literature

23 indexed papers and 2 registered trials mentioning Ipamorelin, straight from PubMed and ClinicalTrials.gov. 2 of 2 administer it; the rest measure it. These have not been read by us. Unlike the studies above, they carry no findings and no limitations written by anyone here, because writing either would mean claiming a reading nobody has done. They are a starting point for yours.

Registered trials (2)

  1. Safety and Efficacy of Ipamorelin Compared to Placebo for the Recovery of Gastrointestinal Function

    Helsinn Therapeutics (U.S.), Inc2011NCT01280344

    interventionalphase2completedn=320

  2. Safety and Efficacy of Ipamorelin for Management of Post-Operative Ileus

    Helsinn Therapeutics (U.S.), Inc2008NCT00672074

    interventionalphase2completedn=117

Papers (23)

  1. Therapeutic peptides in gerontology: mechanisms and applications for healthy aging.

    Mavrych V, et al.Frontiers in aging2026PMID 42021992

    journal articlereview

  2. Injectable Peptide Therapy: A Primer for Orthopaedic and Sports Medicine Physicians.

    Mayfield CK, et al.The American journal of sports medicine2026PMID 41476424

    journal articlereview

  3. Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions.

    Rahman OF, et al.Journal of the American Academy of Orthopaedic Surgeons. Global research & reviews2026PMID 41490200

    journal articlereview

  4. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance.

    Mendias CL, et al.Sports medicine (Auckland, N.Z.)2026PMID 41966639

    journal articlereview

  5. Therapeutic Peptides in Aesthetic, Metabolic and Endocrine Conditions: Effects, Safety, Clinical Applications, and Future Perspectives.

    Renke G, et al.International journal of molecular sciences2026PMID 42123471

    journal articlereview

  6. A new era of doping? Use of peptide and peptide-analog drugs in recreational and professional sport and bodybuilding: a critical review.

    Coutinho LFD, et al.The Journal of sports medicine and physical fitness2026PMID 41880199

    journal articlereview

  7. Peptide Supplements and Their Therapeutic Applications in Sports Medicine.

    Tewari K, et al.The American journal of sports medicine2026PMID 42578445

    journal article

  8. The growth hormone secretagogue receptor 1a agonists, anamorelin and ipamorelin, inhibit cisplatin-induced weight loss in ferrets: Anamorelin also exhibits anti-emetic effects via a central mechanism.

    Lu Z, et al.Physiology & behavior2024PMID 39043357

    journal articleresearch support, non-u.s. gov't

  9. Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males.

    Sinha DK, et al.Translational andrology and urology2020PMID 32257855

    journal articlereview

  10. Attenuation of Visceral and Somatic Nociception by Ghrelin Mimetics.

    N Mohammadi E, et al.Journal of experimental pharmacology2020PMID 32801950

    journal article

  11. Glycine-modified growth hormone secretagogues identified in seized doping material.

    Gajda PM, et al.Drug testing and analysis2019PMID 30136411

    journal article

  12. Analysis of new growth promoting black market products.

    Krug O, et al.Growth hormone & IGF research : official journal of the Growth Hormone Research Society and the International IGF Research Society2018PMID 29864719

    journal articleresearch support, non-u.s. gov't

  13. Structure-activity relationship for peptídic growth hormone secretagogues.

    Ferro P, et al.Drug testing and analysis2017PMID 26811125

    journal article

  14. Detection of GHRP-2 and GHRP-6 in urine samples from athletes.

    Cox HD, et al.Drug testing and analysis2015PMID 25809000

    journal article

  15. Metabolism of growth hormone releasing peptides.

    Thomas A, et al.Analytical chemistry2012PMID 23101768

    journal articleresearch support, non-u.s. gov't

  16. Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus.

    Venkova K, et al.The Journal of pharmacology and experimental therapeutics2009PMID 19289567

    journal articleresearch support, non-u.s. gov't

  17. [Ghrelin-related drugs: clinical perspectives].

    Shimatsu ANihon rinsho. Japanese journal of clinical medicine2004PMID 15506422

    journal articlereview

  18. Influence of chronic treatment with the growth hormone secretagogue Ipamorelin, in young female rats: somatotroph response in vitro.

    Jiménez-Reina L, et al.Histology and histopathology2002PMID 12168778

    journal articleresearch support, non-u.s. gov't

  19. Do growth hormone-releasing peptides act as ghrelin secretagogues?

    Ahnfelt-Rønne I, et al.Endocrine2001PMID 11322495

    comparative studyjournal article

  20. Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats.

    Johansen PB, et al.Growth hormone & IGF research : official journal of the Growth Hormone Research Society and the International IGF Research Society1999PMID 10373343

    journal articleresearch support, non-u.s. gov't

  21. Ipamorelin, the first selective growth hormone secretagogue.

    Raun K, et al.European journal of endocrinology1998PMID 9849822

    journal article

  22. A new series of highly potent growth hormone-releasing peptides derived from ipamorelin.

    Ankersen M, et al.Journal of medicinal chemistry1998PMID 9733495

    journal article

  23. Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption.

    Johansen PB, et al.Xenobiotica; the fate of foreign compounds in biological systems1998PMID 9879640

    comparative studyjournal article

Discussion

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For Research & Educational Discussion Only. Not Medical Advice

This guide is educational reference material compiled from published literature. It is not medical advice, not a recommendation, and not a substitute for a clinician who knows your history. Nothing here should be used to make a decision about your own health without one.

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