Educational reference, not medical advice. This page summarizes information from published research and regulatory filings for educational purposes. It is not a recommendation to use any compound and should not replace guidance from a licensed healthcare provider. Most peptides discussed here are not approved for the uses described.
What it is
GHRP-2 — pralmorelin, also designated KP-102 — is a synthetic hexapeptide (D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH₂) that activates the growth hormone secretagogue receptor (GHSR-1a), the same receptor that binds endogenous ghrelin. It is part of the same family as GHRP-6 (its predecessor) and ipamorelin, and was developed as a more potent successor to GHRP-6 with improved oral, intranasal, and intravenous bioavailability.
History
Cyril Bowers and colleagues at Tulane University developed the original growth hormone-releasing peptides in the late 1970s and early 1980s — work that predated the discovery of ghrelin (the endogenous ligand of GHSR-1a) by nearly two decades. GHRP-6 came first; GHRP-2 was synthesized as a more potent analog and reported in the early 1990s.
Kaken Pharmaceutical in Japan licensed and developed pralmorelin (the international nonproprietary name for GHRP-2) as a single-dose diagnostic agent for growth hormone deficiency. The product was approved in Japan in 2006 as GHRP Kaken 100, a 100 mcg intravenous test injection — a simpler alternative to the multi-step insulin tolerance test for diagnosing adult GH deficiency.
GHRP-2 has never been advanced to FDA approval. A Phase II program in pediatric GH deficiency was conducted in the early 2000s but did not progress to a U.S. registration filing.
Regulatory status
Pralmorelin is approved in Japan as a single-dose diagnostic agent for growth hormone deficiency. It has no approved therapeutic use anywhere, including in Japan.
In the United States, GHRP-2 is not FDA approved and is not on the 503A bulk substances list — compounding pharmacies are not permitted to prepare it for patients. The European Medicines Agency has not authorized it.
The World Anti-Doping Agency lists GHRP-2 under class S2 of the Prohibited List (peptide hormones, growth factors, related substances, and mimetics) — banned in and out of competition. Several anti-doping cases have involved GHRP-2 detection in urine.
Mechanism
Published mechanism papers describe GHRP-2 as a ghrelin-receptor agonist on pituitary somatotrophs and on hypothalamic neurons. Receptor activation on somatotrophs stimulates phospholipase C signaling and growth hormone release; activation on the hypothalamus additionally amplifies GHRH release and suppresses somatostatin tone, producing a larger GH pulse than GHRH alone.
GHRP-2 also raises cortisol and prolactin to a modest degree — less than GHRP-6, more than ipamorelin. The Laferrère et al. 2005 paper demonstrated that GHRP-2, like ghrelin itself, increases food intake in healthy men, consistent with its activity at central ghrelin receptors.
Half-life and dosing intervals
The published plasma half-life of GHRP-2 is short — estimates range from 15 to 60 minutes depending on the route. Subcutaneous, intravenous, intranasal, and oral routes have all been characterized in published pharmacokinetic work, with intravenous and subcutaneous producing the highest peak GH responses.
In the Japanese diagnostic protocol, a single intravenous bolus of 100 mcg is administered and serum GH is measured at 15, 30, 45, and 60 minutes. In observational research use, subcutaneous doses of 100 to 300 mcg are typically described, often given once to three times daily. These doses are extrapolations and are not based on a controlled efficacy trial.
Reconstitution example
GHRP-2 is sold lyophilized in 5 mg or 10 mg vials. A 5 mg vial reconstituted with 2 mL of bacteriostatic water yields 2.5 mg/mL — on a 1 mL U-100 insulin syringe, 10 units (0.1 mL) contains 250 mcg.
A 10 mg vial reconstituted with 2 mL of bacteriostatic water yields 5 mg/mL — 10 units then contains 500 mcg. Vial's calculator handles the unit-to-microgram conversion automatically.
What to know
- Limited approved use. Approval in Japan is restricted to a single-dose diagnostic indication; there are no approved therapeutic uses anywhere.
- Not FDA approved. Compounding pharmacies in the United States are not permitted to prepare GHRP-2 for patients.
- WADA banned. Use is prohibited in competitive sport, and GHRP-2 has been detected in multiple anti-doping cases.
- Hunger and cortisol effects. Unlike ipamorelin, GHRP-2 reliably increases appetite and modestly raises cortisol and prolactin.
- Reported side effects in observational use include increased hunger, transient flushing, water retention, lethargy after injection, and injection-site reactions. Long-term safety has not been characterized in a controlled trial.
- Storage. Lyophilized vials are best stored refrigerated. Once reconstituted, refrigerate and use within 4 weeks per typical supplier stability data.
Sources
- 1.Bowers CY (1998). Growth hormone-releasing peptide (GHRP). Cellular and Molecular Life Sciences.
- 2.Laferrère B et al. (2005). Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men. Journal of Clinical Endocrinology & Metabolism.
- 3.Sigalos JT, Pastuszak AW (2018). The Safety and Efficacy of Growth Hormone Secretagogues. Sexual Medicine Reviews.
- 4.Pandya N et al. (1998). Growth hormone (GH)-releasing peptide-6 requires endogenous hypothalamic GH-releasing hormone for maximal GH stimulation. Journal of Clinical Endocrinology & Metabolism.
- 5.World Anti-Doping Agency — Prohibited List (S2).