Ipamorelin

Ipamorelin is a man-made peptide that acts on the ghrelin receptor to trigger growth hormone release. It was tested as a hospital treatment for slow bowel recovery after surgery, but development stopped and it is not approved as a medicine.

What it is

Ipamorelin is a small synthetic peptide developed by Novo Nordisk researchers in the mid-1990s ^[2]. It belongs to a group called growth hormone secretagogues, which copy the action of the hormone ghrelin ^[2]. It was studied as a possible hospital treatment for postoperative ileus (slow return of bowel function after surgery), but it was never approved ^[2].

Products sold online as ipamorelin are not licensed medicines. They are not made or checked to medicine standards, so their content, purity and sterility are unknown. US anti-doping authorities warn that the safety of experimental peptides sold online, often labelled "not for human use", has not been established ^[4].

How it works

Ipamorelin activates the ghrelin receptor (growth hormone secretagogue receptor). In the pituitary gland this triggers release of growth hormone. Early studies reported that, unlike some related peptides, it does not have major effects on the stress hormones ACTH and cortisol ^[2]. Through ghrelin receptors in the stomach, ghrelin and ghrelin receptor agonists also stimulate stomach acid release and gut movement, which is why it was tested for postoperative ileus ^[2]. In a study in 48 healthy men given ipamorelin by vein, its half-life was about 2 hours ^[2].

Approved medical uses

None in people. Ipamorelin is not approved by the US Food and Drug Administration (FDA), the European Medicines Agency or the UK Medicines and Healthcare products Regulatory Agency (MHRA) for any use. In a 2024 review, the FDA found no data to support its effectiveness for growth hormone deficiency in children or adults ^[2].

What the research shows

• Postoperative ileus: the only efficacy trial in patients that the FDA identified was a phase 2, randomised, placebo-controlled study in 114 adults having bowel surgery. Ipamorelin given by vein did not significantly shorten the time to tolerating solid food compared with placebo, and secondary outcomes such as hospital stay did not differ ^[2]. Clinical development was then discontinued ^[2].
• Growth hormone deficiency: the FDA did not identify any data supporting effectiveness ^[2].
• Product quality: the FDA concluded that ipamorelin is not well characterised. It contains unnatural amino acids, and information on impurities, aggregates and bacterial endotoxins was missing ^{[1, 2]}.
• Other concerns: in animal studies, ghrelin acts on reward areas of the brain. The FDA noted that ipamorelin could, in theory, have similar effects, and that there are possible concerns for reproduction and development. These concerns are based on how the ghrelin system works, not on human data ^[2].
• After this review, the FDA recommended against adding ipamorelin to the list of substances pharmacies may use for compounding ^[2]. It remains on the FDA's list of substances that may present significant safety risks ^[1].

Known risks and side effects

• The FDA reports that a published study identified serious adverse events, including death, when ipamorelin was given by vein for gut motility ^[1].
• Possible immune reactions (immunogenicity) due to aggregates or peptide-related impurities ^{[1, 2]}.
• Unknown content and impurities in products made outside regulated manufacturing ^{[1, 4]}.
• Medicines that raise growth hormone can cause fluid retention, joint pain, carpal tunnel syndrome, raised blood sugar and new diabetes ^[5]. It is not known how often these effects occur with ipamorelin.
• Growth hormone secretagogues, including ipamorelin, are prohibited at all times in sport under the WADA Prohibited List ^[3].

Blood tests commonly monitored

There are no official monitoring guidelines for ipamorelin, because it is not an approved medicine. For the closest approved medicine acting on the growth hormone system, somatropin, the product label recommends monitoring:

• IGF-1 ^[5].
• Blood glucose ^[5].
• Thyroid function and, in people at risk, adrenal function ^[5].

Sources

1. US Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks. Updated April 2026. FDA
2. US Food and Drug Administration. FDA briefing document: Pharmacy Compounding Advisory Committee meeting, 29 October 2024 (ipamorelin and ipamorelin acetate). FDA (PDF)
3. World Anti-Doping Agency. Prohibited List 2026, class S2: peptide hormones, growth factors, related substances and mimetics (English text as reproduced by the German Sport University Cologne). DSHS Cologne
4. US Anti-Doping Agency. 6 things to know about peptide hormones and releasing factors. Updated March 2026. USADA
5. US Food and Drug Administration. Genotropin (somatropin) for injection: prescribing information. Revised 2025. FDA label (PDF)

Related

Last reviewed 7 October 2026. General information, not medical advice. Found a mistake? Email [email protected].