Ipamorelin is one of the most frequently discussed growth-hormone secretagogues in the research-peptide literature, and one of the easiest to over-read. It is a well-characterised pentapeptide agonist of the ghrelin receptor with a cleaner endocrine selectivity profile than earlier GHRPs. That pharmacological fact is not the same thing as a mature clinical evidence base, and it is not the same thing as a UK licence.

This article is a research briefing. It is not a protocol, and it does not authorise or describe human use. Ipamorelin is not a licensed medicine in the United Kingdom. Research-use-only framing applies throughout.

1. Chemistry and origin

Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2) is a pentapeptide developed by Novo Nordisk and first reported by Raun et al. in the European Journal of Endocrinology in 1998. The design goal was to retain GH-releasing activity at GHS-R1a (the ghrelin receptor) while reducing the ACTH, cortisol and prolactin release that complicated GHRP-2 and GHRP-6. In the original characterisation it released GH comparably to GHRP-6 without a measurable ACTH or cortisol rise at GH-releasing exposures. That selectivity is a receptor-level property, not a clinical outcome. Sequence length is five residues; human plasma half-life is short.

2. Mechanism

GHS-R1a is a Gq-coupled receptor on hypothalamic arcuate neurones and pituitary somatotrophs. Endogenous ghrelin is the cognate ligand. Ipamorelin prefers GH release over HPA-axis activation relative to hexarelin and GHRP-2 in the systems tested. Two limits: a GH pulse after a secretagogue is not a GH-replacement regimen; and "less ACTH than GHRP-2" is not "no extra-pituitary activity."

3. Human evidence

Grade: limited beyond the narrow question of whether the peptide releases GH in humans. Gobburu et al. established human PK/PD. Beck et al. 2014 (Int J Colorectal Dis) tested postoperative ileus and did not yield a licensed indication. No contemporary Phase 3 metabolic, sarcopenia or body-composition programme. No MHRA, EMA or NICE appraisal. Popularity is not an evidence tier.

4. Related secretagogues

GHRP-6 and GHRP-2: older, less selective. Hexarelin: potent, additional cardiac and ACTH findings. Sermorelin and CJC-1295: GHRH receptor, not GHS-R1a — combining them is an experimental design, not a licence. Tesamorelin: stronger evidence in an overseas HIV-visceral-adiposity indication; not a ghrelin-receptor agonist; not a UK-licensed comparator.

5. UK legal status

Not an MHRA-authorised medicine. Not, on current public scheduling, a Misuse of Drugs Act controlled drug. Grey-area research peptide: supply as a medicine engages the Human Medicines Regulations 2012. MHRA 2026 research-peptide labelling guidance applies. Listed on the WADA prohibited list as a GH secretagogue — a sporting rule, not an MHRA classification.

6. Quality

A five-residue peptide is cheap to make and easy to adulterate. A usable CoA states sequence or intact mass, chromatogram, method and salt form. Peptide Data does not accept payment for grades.

7. Honest statements

Permissible: selective GHS-R1a pentapeptide (1998); less ACTH/cortisol than GHRP-2 or hexarelin in experimental systems; human PK/PD exists; ileus programme produced no licensed drug; unlicensed in the UK; WADA-prohibited. Not permissible: treatment/cure/prevention claims; interchangeability with recombinant GH; combination protocols; any consumption, reconstitution-for-injection or self-administration instruction.

This article is AI-researched and editorially reviewed. It is provided for research and educational purposes only and is not medical advice. Research peptides are not licensed for human consumption in the UK.