Head-to-head comparison
| Property | GHRP-2 | Ipamorelin |
|---|---|---|
| Category | Muscle & Growth | Muscle & Growth |
| Legal Status | Reclassification Pending | Reclassification Pending |
| Primary Route | subcutaneous | subcutaneous |
| Half-life | ~15 minutes (plasma) | ~2 hours |
| Mol. Weight | 817.97 Da | 711.85 Da |
| Side Effects | Mild increased appetite, Transient cortisol elevation, Transient prolactin elevation | Headache, Flushing, Injection site pain |
Key differences
- Selectivity: Ipamorelin is highly selective for GH release with minimal effects on cortisol, ACTH, or prolactin; GHRP-2 produces transient cortisol and prolactin elevation alongside GH release.
- Appetite effects: Ipamorelin has minimal appetite stimulation due to low ghrelin mimicry; GHRP-2 causes mild increased appetite through hypothalamic neuropeptide Y (NPY) neuron activation, though less than GHRP-6.
- Potency: GHRP-2 is considered more potent for raw GH secretion, particularly when combined with somatostatin suppression; ipamorelin produces a cleaner but potentially lower-magnitude GH pulse.
- Half-life: Ipamorelin has a half-life of approximately 2 hours; GHRP-2 has a plasma half-life of approximately 15 minutes, requiring more frequent dosing for sustained GH elevation.
- Clinical use: GHRP-2 is approved in Japan as a diagnostic agent for GH deficiency (100 mcg IV bolus); ipamorelin has Phase II clinical trial data but no regulatory approval in any market.
- Dosing: Ipamorelin is commonly dosed at 200-300 mcg subcutaneously 2-3 times daily; GHRP-2 at 100-300 mcg subcutaneously 2-3 times daily, often paired with a GHRH analog.
- Legal status: Both are under FDA reclassification review. GHRP-2 was placed on the FDA Category 2 bulk drug substance list in September 2023 and is expected to remain restricted; ipamorelin is also reclassification-pending.
The verdict
Ipamorelin and GHRP-2 sit at different points on the selectivity-potency tradeoff. Ipamorelin is the preferred choice for users who prioritize a clean hormonal profile with minimal cortisol and prolactin disruption, making it better suited for anti-aging and long-term protocols. GHRP-2 delivers stronger raw GH secretion and has the advantage of an approved clinical use (GH deficiency diagnosis in Japan), but its cortisol and prolactin elevation and shorter half-life make it less convenient for sustained use. Neither has completed large-scale human clinical trials for body composition outcomes.
Frequently asked questions
GHRP-2 is generally considered to produce a stronger GH secretory response than ipamorelin, particularly when somatostatin tone is suppressed. However, GHRP-2 achieves this with off-target effects on cortisol and prolactin that ipamorelin avoids. The net benefit depends on whether raw GH magnitude or hormonal cleanliness is prioritized.
GHRP-2 causes more appetite stimulation than ipamorelin. GHRP-2 activates hypothalamic NPY neurons, producing mild hunger, though significantly less than GHRP-6. Ipamorelin has minimal ghrelin mimicry and typically does not noticeably increase appetite at standard doses.
Combining two ghrelin receptor agonists is uncommon because they compete for the same receptor (GHSR-1a). More typical protocols stack either ipamorelin or GHRP-2 with a GHRH analog like CJC-1295 or Mod GRF 1-29, which acts on the separate GHRH receptor to amplify GH release synergistically.
Ipamorelin has fewer off-target effects. It does not significantly elevate cortisol, ACTH, or prolactin at standard doses and has minimal appetite impact. GHRP-2 causes transient cortisol and prolactin elevation, mild appetite increase, water retention, and flushing. Both cause headache and injection site reactions.
Both are under FDA reclassification review. GHRP-2 was specifically placed on the FDA Category 2 bulk drug substance list in September 2023, banning compounding pharmacy preparation in the US. Industry analysis suggests GHRP-2 is more likely to remain restricted than ipamorelin due to its cortisol and prolactin elevation concerns.