Overview
GHRP-2 (Growth Hormone Releasing Peptide-2) is a synthetic hexapeptide that acts as a potent agonist at the ghrelin receptor (GHSR-1a). It was one of the first synthetic GH secretagogues developed, with research dating to the early 1990s, and served as an important tool for understanding the ghrelin receptor system before ghrelin itself was discovered in 1999.
Among the GHRP family, GHRP-2 is considered the most potent GH releaser and has been studied more extensively in clinical settings than most other GHRPs — including a Japanese Phase III trial under the name Pralmorelin for diagnosis of GH deficiency. Unlike Ipamorelin, GHRP-2 produces meaningful co-stimulation of cortisol and prolactin, which may limit its appeal for long-term use but makes it among the best-characterized compounds in the class.
Mechanism of Action
GHSR-1a Agonism (Ghrelin Receptor): GHRP-2 binds to and activates the ghrelin receptor on pituitary somatotrophs, triggering robust GH secretion through a calcium-dependent intracellular pathway. The ghrelin receptor is G-protein coupled (Gq), and GHRP-2’s activation of this pathway is both rapid and potent.
HPA Axis Cross-Activation: Unlike Ipamorelin, GHRP-2 produces dose-dependent increases in ACTH and cortisol — a consequence of GHSR-1a expression in the hypothalamic-pituitary-adrenal axis. This limits its ideal for chronic use but is well-characterized and predictable.
Synergy with GHRH: Combined with GHRH analogs, GHRP-2 produces synergistic GH release exceeding either compound alone — the mechanistic basis for common research stacks.
Clinical Research & Evidence
Evidence Level: 🟡 EL2 — Phase III data (diagnostics); off-label research use
| Study | N | Key Finding |
|---|---|---|
| Pralmorelin Phase III (Japan) | ~150 | Validated as GH stimulation test; sensitivity/specificity for GH deficiency diagnosis |
| Arvat et al. 1998 | 16 | GHRP-2 dose-dependently increased GH in elderly and young; elderly showed blunted response |
| Mericq et al. 2003 | Children | GHRP-2 + GHRH superior to GHRH alone for GH secretion in GH-deficient children |
Pralmorelin: Approved in Japan as a diagnostic agent (GH stimulation test) — giving GHRP-2 a regulatory approval footprint, though limited to diagnostic use, not therapeutic.
Research-Referenced Dosing Protocols
- 100–300 mcg subcutaneous injection, 1–3x daily
- Often combined with CJC-1295 100 mcg for synergistic GH pulse
- Timing: before bed, upon waking, and/or pre-workout
- Fasted injection recommended (food — especially glucose and fatty acids — blunts GH response)
Side Effects & Contraindications
Compared to Ipamorelin:
- More significant cortisol elevation (dose-dependent)
- More prolactin elevation
- Greater hunger stimulation (ghrelin effect)
- Tingling extremities, water retention, headache
Practical concern: Chronic cortisol elevation from frequent dosing may offset some of the anabolic/body composition benefits sought from GH stimulation.
Contraindications:
- Active malignancy
- Diabetes (cortisol elevation worsens insulin resistance)
- Pregnancy
Legal & Regulatory Status
| Region | Status |
|---|---|
| Japan | Approved as Pralmorelin (diagnostic use only) |
| United States | Not FDA approved; research chemical |
| WADA | Prohibited (GH secretagogues) |
Research Citations
- Arvat E, et al. Preliminary evidence that GH-releasing peptide-2 activates GH/IGF-I axis in humans. J Endocrinol Invest. 1998.
- Mericq V, et al. Effects of eight months treatment with graded doses of a growth hormone (GH)-releasing peptide. J Clin Endocrinol Metab. 2003.
- Bowers CY, et al. On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary. Endocrinology. 1984.