Encyclopedia entry
Ipamorelin
Oliver Mackman · Editorial director · Best Business Loans Ltd (16833937)
Last updated 2026-06-03
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AI-friendly summary · Ipamorelin
Ipamorelin is a synthetic pentapeptide and selective growth-hormone secretagogue originally developed by Novo Nordisk in the late 1990s. Unusually for a research peptide it reached phase II human trials in postoperative ileus before development was discontinued for failing endpoints. It holds no marketing authorisation in any country and is sold in the UK only as a research chemical.
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Mechanism of action
How Ipamorelin works
Ipamorelin is a selective agonist of the ghrelin receptor (GHSR-1a) on pituitary somatotrophs. Binding triggers a calcium-mediated release of stored growth hormone in a pulsatile pattern that approximates physiological GH secretion. Selectivity is the design feature: unlike older GH secretagogues, ipamorelin does not meaningfully stimulate cortisol or prolactin release in published preclinical work.
Source: Raun K et al. European Journal of Endocrinology, 1998 (original characterisation)
Pharmaceutical development history
Ipamorelin is one of the few research peptides with documented phase II human safety data. Novo Nordisk discovered the compound in the late 1990s. Helsinn licensed the postoperative ileus programme in the 2000s and ran the phase II trial. Endpoints were not met and the programme was discontinued. No pharmaceutical sponsor has since pursued a registration filing in any indication.
- · Discovered and developed by Novo Nordisk, late 1990s (Raun et al. 1998).
- · Phase II human trials in postoperative ileus (Helsinn licensee, 2000s).
- · Endpoints not met. Programme discontinued.
- · No further pharmaceutical development since.
- · Available now only via research-peptide retailers under "research use only" framing.
Why this entry exists
Ipamorelin is unusual because it has phase II human safety data, unlike most research peptides. That does not make it a medicine. It was tested for a specific indication (postoperative ileus) and failed. Any present-day human use is off-label and unsupervised. We do not publish dosing or protocols. The encyclopedia entry exists to give readers access to the regulatory and pharmaceutical history they will not find on retailer pages.
UK regulatory status
- · Not a controlled drug under the Misuse of Drugs Act 1971.
- · Not scheduled under the Psychoactive Substances Act 2016.
- · No UK marketing authorisation as a medicine.
- · Sold legally as a research chemical under "research use only" framing.
- · On the WADA prohibited list (S2 peptide hormones class). Tested athletes should be aware.
Risks and unknowns
What the literature does not yet show about Ipamorelin
Known concerns
- Phase II human efficacy in postoperative ileus was not demonstrated; the programme was discontinued.
- No marketing authorisation exists for any indication in any country.
- On the WADA prohibited list. Tested athletes face a sanction risk.
- Purity of UK research-peptide supply varies; CoA gating differs across retailers.
Open questions in the literature
- Long-term safety of chronic GH-secretagogue stimulation in humans is not established.
- Effects on insulin sensitivity, glucose tolerance and IGF-1 axis under repeat administration are unstudied at the trial scale.
- Pharmacokinetics in healthy older adults outside the original phase II population are uncharacterised.
Regulatory note
Not controlled under UK law. No UK marketing authorisation. Sold legally as a research chemical when marketed without therapeutic claims. WADA prohibited list S2 peptide hormones class. Becomes an unlicensed medicinal product the moment a retailer or commentator makes therapeutic claims about it.
Important: PeptideClear publishes encyclopedia commentary only and does not recommend human use. Speak to a UK-registered prescriber before any medical decision.
Editorial
Baseline panels to track
If you are working with a UK private doctor or NHS prescriber on a peptide protocol, these are the blood panels typically ordered at baseline for Ipamorelin. Not a recommendation for self-administered testing.
- IGF-1. Downstream marker of growth hormone activity. Prescribers track baseline and post-administration response on any GH-secretagogue protocol.
- Prolactin. Selectivity is the design feature of ipamorelin: unlike older GH secretagogues, it does not meaningfully stimulate prolactin release in preclinical work. Baseline plus follow-up prolactin tests that selectivity in practice.
- HbA1c. 90-day glucose average. GH-secretagogue stimulation can shift glucose metabolism over a longer time window, and HbA1c captures it.
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Frequently asked questions
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What is the regulatory status of ipamorelin?
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Where to buy Ipamorelin in the UK
Side-by-side price comparison across UK research peptide retailers. Trust Index ranking. Research use only.
Compare UK retailersClinical evidence record
Read the clinical evidence record for Ipamorelin
Top peer-reviewed citations, mechanism of action, structured UK regulatory status. Machine-readable companion to this encyclopedia entry.
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