Summary
Ipamorelin is a five-residue ghrelin-receptor agonist described in 1998 as the first selective growth hormone secretagogue. In animals it released GH without the rise in cortisol and prolactin seen with earlier GHRPs. In people, a phase 2 trial for bowel recovery after surgery did not show a benefit.
Structure
Aib-His-D-2Nal-D-Phe-Lys-NH2, a pentapeptide containing non-standard amino acids.
How it works
Ipamorelin activates GHS-R1a, the ghrelin receptor, on the pituitary and hypothalamus. Unlike GHRP-6 and GHRP-2, it had little effect on ACTH or cortisol even at high doses in animal studies.
Research use cases
Areas where Ipamorelin has been studied. Inclusion here does not mean it works for that purpose.
- GH release studies
- Postoperative ileus (phase 2)
- Bone growth in animal models
What the research found
Selectivity
In pigs and rats, ipamorelin released GH with potency similar to GHRP-6, but did not raise ACTH or cortisol beyond levels seen with GHRH, even at doses more than 200 times the GH-releasing dose.1
Postoperative ileus
In 114 patients after bowel resection, intravenous ipamorelin did not significantly shorten time to recovery of gastrointestinal function compared with placebo.2
Safety and open questions
Well tolerated in the phase 2 trial. Like other ghrelin agonists, it may increase appetite and affect glucose metabolism.
Regulatory status
Not approved. A phase 2 trial for postoperative ileus did not meet its endpoint. Named in the February 2026 HHS compounding announcement.
Status was accurate when this page was last reviewed on October 26, 2026. Regulations change; check with the relevant authority before relying on it.
Ipamorelin: common questions
Why is ipamorelin called selective?
Earlier GHRPs also released cortisol and prolactin. Ipamorelin’s GH release was not accompanied by those hormones in animal studies, which is where the term comes from.
Is Ipamorelin approved for human use?
Not approved. A phase 2 trial for postoperative ileus did not meet its endpoint. Named in the February 2026 HHS compounding announcement.
References
- Raun K, Hansen BS, Johansen NL, et al. (1998). Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology.
- Beck DE, Sweeney WB, McCarter MD; Ipamorelin 201 Study Group. (2014). Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. International Journal of Colorectal Disease.
Links open a PubMed search for the exact title, or the original source where one is given.