Ipamorelin: Growth Hormone Secretagogue Research Review
Ipamorelin is a pentapeptide growth hormone secretagogue notable for its selective stimulation of GH release without significant co-stimulation of cortisol, prolactin, or ACTH — a profile that distinguishes it from earlier GHRPs.
This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making any health decisions.
What Is Ipamorelin?
Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2) is a synthetic pentapeptide and selective growth hormone secretagogue (GHS). It was developed in the late 1990s as part of a research programme to identify GH-releasing peptides with improved selectivity profiles compared to earlier compounds such as GHRP-2 and GHRP-6.
Its key distinguishing characteristic in preclinical studies is the selective stimulation of GH release from pituitary somatotrophs without significant co-stimulation of ACTH, cortisol, or prolactin — a selectivity profile that has made it a widely used research tool for studying GH axis regulation.
Molecular Profile
| Property | Value | |----------|-------| | Molecular Formula | C38H49N9O5 | | Molecular Weight | 711.87 Da | | CAS Number | 170851-70-4 | | Sequence | Aib-His-D-2-Nal-D-Phe-Lys-NH2 | | Receptor | Ghrelin receptor (GHSR-1a) |
Mechanism of Action
Ipamorelin acts as an agonist at the ghrelin receptor (GHSR-1a), a G-protein coupled receptor expressed predominantly in the hypothalamus and pituitary gland. Receptor activation triggers a cascade involving phospholipase C, IP3, and intracellular calcium mobilisation, ultimately stimulating GH secretion from anterior pituitary somatotrophs.
Unlike endogenous ghrelin, Ipamorelin does not significantly stimulate appetite-related pathways at research doses, and unlike GHRP-6, it does not produce the pronounced cortisol and prolactin co-stimulation observed with that compound.
Selectivity Comparison
| Compound | GH Release | Cortisol | Prolactin | ACTH | |----------|-----------|----------|-----------|------| | GHRP-2 | +++ | ++ | + | ++ | | GHRP-6 | +++ | +++ | ++ | +++ | | Ipamorelin | +++ | − | − | − | | Hexarelin | ++++ | +++ | ++ | +++ |
Based on published in vivo rodent and primate studies. +++ = significant stimulation, − = minimal/no stimulation.
Key Research Findings
GH Pulse Amplitude Studies in rats and pigs demonstrated that Ipamorelin produced dose-dependent increases in GH pulse amplitude comparable to GHRP-2, without the adrenal axis stimulation. This selectivity has been confirmed in primate models.
Bone Density Research A notable series of studies examined Ipamorelin's effects on bone mineral density in ovariectomised rats. Researchers reported significant increases in tibial bone density and periosteal bone formation in treated animals compared to controls.
Combination with CJC-1295 Ipamorelin is frequently studied in combination with CJC-1295 (a GHRH analogue) to examine synergistic GH release. The combination targets both the GHRH receptor and the ghrelin receptor simultaneously, producing amplified GH pulses in animal models.
Research Quality Standards
For reproducible GH axis research, Ipamorelin purity is critical:
- HPLC purity ≥98% minimum; ≥99% preferred for receptor binding studies
- Mass spectrometry confirmation (expected MW: 711.87 Da)
- Endotoxin testing (critical for in vivo studies)
- Lyophilized format for stability
Pure Peptides supplies Ipamorelin at ≥99.6% HPLC purity.
Research use only. Not for human administration.