Understand the source comparison
Hexarelin vs GHRP-2, GHRP-6, and Ipamorelin: Potency and Selectivity
All four peptides belong to the growth hormone-releasing peptide (GHRP) class, but their receptor affinity profiles and off-target effects differ enough to matter in research design. GHRP-6 was the first synthetic ghrelin mimetic—it produces moderate GH releas
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- All four peptides belong to the growth hormone-releasing peptide (GHRP) class, but their receptor affinity profiles and off-target effects differ enough to matter in research design. GHRP-6 was the first synthetic ghrelin mimetic—it produces moderate GH release (peak plasma levels around 8–12 ng/mL at 100 mcg) but triggers significant appetite stimulation and prolactin co-secretion, making it poorly suited for metabolic studies where food intake must remain controlled. GHRP-2 refined the structure to reduce appetite effects while maintaining strong GH output (10–15 ng/mL), but it still elevates cortisol and prolactin alongside GH.
- Hexarelin pushed potency higher—15–25 ng/mL peak GH at the same 100 mcg dose—but with even stronger cortisol co-release (plasma cortisol increases 40–60% above baseline 90 minutes post-dose). That cortisol spike is a catabolic signal that can interfere with anabolic research endpoints, which is why ipamorelin was developed as a selective GH secretagogue. Ipamorelin produces 8–12 ng/mL peak GH with minimal cortisol, prolactin, or appetite effects—it's the cleanest GHRP for isolating GH-specific outcomes, but it's also the least potent by absolute amplitude.
- In our experience working with research teams comparing these peptides, the hierarchy breaks down like this: hexarelin for maximum acute GH pulse, GHRP-2 for balanced potency with manageable side-effect profile, ipamorelin for chronic protocols where receptor selectivity and repeatability matter more than raw amplitude. GHRP-6 is rarely used in contemporary research unless appetite stimulation is an intentional endpoint.