Growth hormone axis

Ipamorelin

Reviewed 22 October 2026 · How we research

Also known as: Ipa, NNC 26-0161

What is Ipamorelin?

Ipamorelin is a five-amino-acid peptide that triggers growth-hormone release by activating the ghrelin receptor (GHS-R1a). It was described in 1998 as the first selective growth-hormone secretagogue: unlike older compounds such as GHRP-6 and GHRP-2, it raises growth hormone without substantially raising cortisol, ACTH or prolactin, and with little effect on appetite.

That selectivity is why it is the most common partner for CJC-1295 in research blends.

How Ipamorelin works

Ghrelin, the “hunger hormone”, also stimulates growth hormone through GHS-R1a receptors in the pituitary and hypothalamus. Ipamorelin mimics this specific action. Each dose produces a distinct GH pulse, peaking within about 30–60 minutes. Pairing it with a GHRH analogue (like CJC-1295) amplifies the pulse because the two pathways are synergistic.

What the research shows

In pigs, ipamorelin released growth hormone with potency similar to GHRP-6 but without raising ACTH or cortisol, even at 200 times the effective dose (Raun et al., 1998).
Rodent studies showed increased longitudinal bone growth and bone mineral content.
Phase 2 trials as an intravenous treatment for postoperative ileus (gut paralysis after surgery) were well tolerated but did not meet their primary endpoint.

Compare: Tesamorelin vs Ipamorelin · CJC-1295 vs Ipamorelin

Ipamorelin side effects

In the postoperative ileus trials, adverse events were similar to placebo. Commonly reported effects in non-clinical use include headache, flushing, water retention and injection-site irritation. Raised GH and IGF-1 may reduce insulin sensitivity.

UK legal status

Ipamorelin is not licensed in the UK or elsewhere. It is sold only as a research chemical and is banned by WADA as a growth-hormone secretagogue.

More detail, including current UK research-vial prices: Ipamorelin UK guide. For the doses used in published studies and the reconstitution maths: Ipamorelin dosing in the literature.

Ipamorelin: frequently asked questions

What does ipamorelin do?

It activates the ghrelin receptor to trigger a pulse of growth hormone release, without the large cortisol and prolactin rises seen with older secretagogues.

Does ipamorelin increase appetite?

Much less than GHRP-6 or GHRP-2. Its selectivity is the main reason it is studied in place of those older peptides.

What is CJC-1295/ipamorelin?

A blend of the no-DAC GHRH analogue CJC-1295 with ipamorelin. The two act on different receptors and together produce a larger growth-hormone pulse.

Is ipamorelin safe?

It was well tolerated in short hospital trials, but long-term human safety has not been studied.

References

Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139:552–561.
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.

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