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What Is GHRP-2?
GHRP-2 (Growth Hormone Releasing Peptide-2, also known as KP-102 or Pralmorelin) is a synthetic hexapeptide growth hormone secretagogue. It's considered one of the most potent GH-releasing peptides while producing less appetite stimulation than GHRP-6, making it a middle-ground option among the GHRPs.
GHRP-2 has actually been approved in Japan under the name Pralmorelin for diagnostic use in assessing GH deficiency, giving it more clinical validation than many other research peptides.
Key Characteristics
- GH Release: Very potent (among strongest GHRPs)
- Appetite: Moderate increase (less than GHRP-6)
- Cortisol: Moderate increase
- Prolactin: Notable increase
- Status: Approved in Japan for diagnostics
Mechanism of Action
Ghrelin Receptor Agonism
GHRP-2 works primarily through the ghrelin receptor:
- Binds to GHS-R1a (ghrelin/growth hormone secretagogue receptor)
- Stimulates GH release from anterior pituitary
- Also acts on hypothalamic GHRH neurons
- Amplifies natural GH pulses
Multi-Site Action
Research suggests GHRP-2 acts at multiple levels:
- Pituitary: Direct somatotroph stimulation
- Hypothalamus: Increases GHRH release
- Hypothalamus: May suppress somatostatin (GH inhibitor)
Hormone Profile
GHRP-2's effects on various hormones:
- GH: Strong, dose-dependent release
- IGF-1: Secondary increase from elevated GH
- Cortisol: Transient elevation (~20-50%)
- Prolactin: More pronounced than GHRP-6
- ACTH: Mild increase
Research Findings
GH Release Studies
- Consistent, robust GH release across studies
- Peak GH within 15-30 minutes
- Higher peak GH than GHRP-6 in some comparisons
- Maintained efficacy with chronic administration
Diagnostic Applications
Approved in Japan for GH deficiency testing:
- Used to assess pituitary GH secretion capacity
- Alternative to traditional GH stimulation tests
- Well-characterized dose-response relationship
- Provides clinical-grade safety data
Body Composition Research
- Potential improvements in lean body mass
- Possible fat mass reduction
- Effects require consistent, extended use
- Synergistic with exercise and nutrition
Sleep Research
- May enhance GH release during sleep
- Potential for improved sleep quality
- Night-time dosing common in research protocols
Key Published Research
| Year | Focus | Key Finding | Reference |
|---|---|---|---|
| 1997 | GH release | Dose-response characterization | Bowers et al. |
| 2001 | Diagnostic use | Validated for GH testing | Takano et al. (Japan) |
| 2008 | Comparison study | Compared GHRPs head-to-head | Svensson et al. |
| 2015 | Long-term effects | Sustained efficacy observed | Various authors |
GHRP-2 vs GHRP-6 vs Ipamorelin
| Feature | GHRP-2 | GHRP-6 | Ipamorelin |
|---|---|---|---|
| GH release potency | Very high | Very high | High |
| Appetite increase | Moderate | Strong | Minimal |
| Cortisol elevation | Moderate | Moderate | None |
| Prolactin elevation | Notable | Moderate | None |
| Clinical approval | Yes (Japan) | No | No |
Position Among GH Secretagogues
GHRP-2's Niche
GHRP-2 occupies a middle position:
- More potent GH release than ipamorelin
- Less appetite stimulation than GHRP-6
- More prolactin elevation than either
- Japanese approval provides credibility
- Often chosen when maximum GH is desired with acceptable side effects
Administration in Research
- Route: Subcutaneous or intravenous
- Research doses: 100-300 mcg per injection
- Frequency: 2-3 times daily typical
- Timing: Pre-meal and/or before sleep
- Half-life: ~15-25 minutes
- Saturation dose: ~100-200 mcg (beyond which little additional GH)
Side Effects and Considerations
- Appetite increase: Present but manageable for most
- Water retention: Possible, especially initially
- Prolactin elevation: Monitor if using long-term
- Cortisol increase: Transient with each dose
- Tiredness: Some report post-injection fatigue
- Tingling: Common at injection site
Research Status
While GHRP-2 is approved in Japan for diagnostic use (as Pralmorelin), it is not FDA-approved in the United States. Outside Japan, it remains a research compound. The Japanese approval does provide valuable clinical safety and efficacy data that many other GHRPs lack.
Summary
GHRP-2 represents a powerful option in the GHRP family, offering potent GH release with moderate side effects. Its approval in Japan for diagnostic purposes provides clinical validation rare among research peptides. The moderate appetite stimulation (compared to GHRP-6) and strong GH release make it attractive for researchers seeking robust results with acceptable trade-offs. The prolactin elevation is the primary consideration for long-term research protocols.