Overview
GHRP-2 (Growth Hormone Releasing Peptide-2) and Ipamorelin are both synthetic growth hormone secretagogues (GHS) that activate the ghrelin receptor GHS-R1a in the pituitary and hypothalamus. Despite sharing this primary mechanism, they differ substantially in receptor selectivity, magnitude of GH release, and off-target hormonal effects — differences that matter significantly in research protocol design.
Mechanism Comparison
GHRP-2 (D-Ala-D-β-Nal-Ala-Trp-D-Phe-Lys-NH₂, MW 817.99 Da) is a first-generation hexapeptide GHS that produces strong GH pulses but with notable co-stimulation of cortisol, prolactin, and ACTH. This broader receptor engagement reflects GHS-R1a activity plus partial binding at CD36 and other receptors. GHRP-2 also stimulates appetite via central ghrelin pathways, which can confound metabolic research endpoints.
Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH₂, MW 711.85 Da) is a pentapeptide engineered for high selectivity. It produces robust GH pulses comparable in amplitude to GHRP-2 while demonstrating negligible effects on cortisol, prolactin, or ACTH at research-relevant doses. This selectivity makes Ipamorelin the preferred GHS in studies where hormonal confounders need to be minimized.
Key Differences
| Parameter | GHRP-2 | Ipamorelin |
|---|---|---|
| Generation | First | Third |
| Molecular weight | 817.99 Da | 711.85 Da |
| GH pulse amplitude | High | High (comparable) |
| Cortisol stimulation | Significant | Minimal |
| Prolactin elevation | Yes | No |
| Appetite stimulation | Yes | Minimal |
| Receptor selectivity | Moderate | High |
Research Applications
GHRP-2 is used in research where maximal GH pulse stimulation is the primary endpoint and where cortisol co-elevation is acceptable or desired (e.g., stress-response studies). Ipamorelin is preferred in longevity, body composition, and GH-axis studies where clean GH elevation without cortisol confounding is needed. Ipamorelin is also the standard comparator in GHS combination studies with CJC-1295 (No DAC) due to its predictable, selective profile.
Laboratory Considerations
Both peptides are supplied as lyophilized powder and reconstituted with bacteriostatic water (0.9% benzyl alcohol). GHRP-2 is supplied as 5mg vials; Ipamorelin as 5mg vials. Both are stable at 4°C for 3–4 weeks post-reconstitution and at −20°C for up to 3 months. Standard peptide handling applies — avoid repeated freeze-thaw cycles and protect from light.
Research Disclaimer: All compounds discussed are intended exclusively for laboratory and research purposes. This content is not medical advice. Bastion Peptides products are not approved for human use, consumption, or therapeutic application.
