Ipamorelin vs GHRP-2: Selecting the Right Growth Hormone Secretagogue

Ipamorelin and GHRP-2 are both GHS-R1a agonists that stimulate GH release, and both are commonly combined with GHRH analogues like Sermorelin or CJC-1295. Their key difference is in hormonal selectivity — a difference with meaningful research design implications.

GH Release Potency

GHRP-2 has approximately 10-fold higher GHS-R1a binding affinity than ipamorelin, producing correspondingly higher peak GH amplitudes.

In Raun K et al. (*European Journal of Endocrinology*, 1998) direct comparison (rats):

• Peak GH: Ipamorelin ~400 ng/mL vs GHRP-2 ~500 ng/mL at equivalent doses
• GHRP-2 produces approximately 15-25% higher GH peaks

The Cortisol Difference: The Key Distinction

At GH-stimulating doses, per Arvat E et al. (*JCEM*, 1997):

• [GHRP-2](/peptides/ghrp-2): Elevates ACTH ~2.4× and cortisol ~1.8× above baseline
• [Ipamorelin](/peptides/ipamorelin): No measurable cortisol or ACTH elevation at any GH-stimulating dose

This matters in body composition and tissue healing research models, where unwanted cortisol elevation (catabolic: muscle protein breakdown, adipogenesis promotion, immune suppression) represents a significant confound.

GHRP-2 also produces mild prolactin elevation (~1.5×); ipamorelin does not.

Appetite Stimulation

Both peptides activate GHS-R1a (the ghrelin receptor). GHRP-2 produces moderate appetite stimulation in most subjects; ipamorelin produces mild appetite in approximately 40-50% of subjects. For research models where caloric intake is a controlled variable, Ipamorelin's weaker appetite effect is preferable.

Research Selection Guide

For most combination protocols with CJC-1295 or Sermorelin, ipamorelin's cleaner profile makes it the default choice.

Both compounds are research peptides not approved for human therapeutic use.