Written by PX1 Research Team
PX1 chemists and research educators with hands-on experience in US-based peptide manufacturing, HPLC / mass-spectrometry lot testing, and endotoxin QC. All content is citation-backed and peer-reviewed for accuracy.
The Complete Guide to Ipamorelin Research
Research Guide
Reviewed By
PX1 QC — Analytical Chemistry Team
Every article is reviewed by PX1's in-house analytical team for accuracy on mechanism, dosing ranges reported in the literature, and lab-handling guidance. We do not publish clinical or medical advice.
Quick answer
Ipamorelin is a selective growth hormone secretagogue pentapeptide. Mechanism, selectivity vs older GHRPs, published research, handling, and purity verification.
Key takeaways
- GH release comparable to GHRP-6 in pituitary cell studies
- No significant effect on ACTH, cortisol, or prolactin at doses well above those needed for GH release — a selectivity profile its developers highlighted as its defining property
- Minimal effect on appetite relative to GHRP-6 in preclinical models
- Bone growth studies: in rodent models, ipamorelin administration was associated with increased longitudinal bone growth and body weight gain consistent with elevated GH/IGF-1
What Ipamorelin is
Ipamorelin is a synthetic pentapeptide (five amino acids: Aib-His-D-2-Nal-D-Phe-Lys-NH2) belonging to the growth hormone secretagogue family. It acts as a ghrelin receptor (GHS-R1a) agonist — the same receptor the hunger hormone ghrelin uses — triggering growth hormone release from the pituitary.
It was first described in the late 1990s by Novo Nordisk researchers and remains one of the most-studied selective GH secretagogues in the preclinical literature.
Why researchers consider it "selective"
The older growth hormone releasing peptides — GHRP-6 and GHRP-2 — stimulate GH release but also raise cortisol and prolactin at commonly studied doses, and GHRP-6 in particular increases appetite strongly. Ipamorelin was developed specifically to avoid those off-target effects:
- GH release comparable to GHRP-6 in pituitary cell studies
- No significant effect on ACTH, cortisol, or prolactin at doses well above those needed for GH release — a selectivity profile its developers highlighted as its defining property
- Minimal effect on appetite relative to GHRP-6 in preclinical models
That clean pharmacology is why ipamorelin is the GHRP most often chosen for controlled GH-axis research.
Research findings
Published preclinical work on ipamorelin includes:
- Bone growth studies: in rodent models, ipamorelin administration was associated with increased longitudinal bone growth and body weight gain consistent with elevated GH/IGF-1
- GI motility research: ipamorelin was investigated clinically as an accelerant of postoperative gastric motility (Phase 2, postoperative ileus), where the primary endpoint was not met and development for that indication was discontinued — a useful reminder that GH secretagogue activity does not translate to every proposed indication
- Selectivity confirmation: human volunteer dosing confirmed GH release without the cortisol/prolactin elevations seen with older GHRPs
Structure and handling
| Property | Value |
|---|---|
| Sequence length | 5 amino acids (pentapeptide) |
| Molecular formula | C38H49N9O5 |
| Molar mass | ≈ 711.9 g/mol |
| Receptor target | GHS-R1a (ghrelin receptor) |
| Presentation | Lyophilized powder |
Ipamorelin is supplied lyophilized. Sealed vials stored at -20°C are stable long-term; reconstituted solutions (bacteriostatic water) should be kept at 2–8°C and used within a few weeks. As with all peptides, avoid repeated freeze-thaw cycles.
Purity considerations
A pentapeptide is short and relatively easy to synthesize, which means crude synthesis byproducts (truncated sequences) are the most common impurity class. Verify HPLC ≥99% with a visible chromatogram and mass-spec identity on the lot COA before use.
Research use only. Ipamorelin is not approved for human use; all applications are investigational.