A 6-amino-acid synthetic growth hormone secretagogue that sits between GHRP-6 and ipamorelin in terms of selectivity. Produces strong GH release with moderate cortisol and prolactin elevation. FDA-approved in Japan as a GH deficiency diagnostic (pralmorelin).
GHRP-2 (D-Ala-D-BNal-Ala-Trp-D-Phe-Lys-NH2), also known as pralmorelin, is a second-generation hexapeptide GH secretagogue. It was developed to improve upon GHRP-6's selectivity while maintaining potent GH release.
GHRP-2 is notable as the only GHRP with regulatory approval anywhere in the world — it is approved in Japan as pralmorelin for the diagnosis of growth hormone deficiency (the GHRP-2 stimulation test). Its moderate selectivity profile places it between the non-selective GHRP-6 and the highly selective ipamorelin.
GHRP-2 (also known as pralmorelin) is the most widely studied growth hormone-releasing peptide in the GHRP family and the only one to achieve regulatory approval anywhere in the world — it is approved in Japan as a diagnostic agent for GH deficiency under the trade name GHRP Kaken. Developed in the 1990s, GHRP-2 acts as a synthetic ghrelin mimetic, binding to the growth hormone secretagogue receptor (GHS-R1a) and stimulating GH release from the anterior pituitary.
GHRP-2 occupies a middle ground in the selectivity spectrum of GH secretagogues: it is more selective than GHRP-6 (which strongly stimulates appetite and cortisol) but less selective than ipamorelin (which has minimal non-GH hormonal effects). GHRP-2 produces robust GH pulses with moderate appetite stimulation and mild cortisol/prolactin elevation — a trade-off that some clinicians find acceptable given its potent GH-releasing capacity.
GHRP-2's mechanism is fundamentally the same as other GHRPs — GHS-R1a activation leading to GH release. Its improved selectivity over GHRP-6 comes from subtle differences in receptor binding kinetics due to the D-beta-naphthylalanine residue, which provides a bulkier aromatic interaction in the receptor binding pocket.
| Pathway | Effect | Significance |
|---|---|---|
| GH release | Potent GHS-R1a agonism on somatotrophs | Strong, dose-dependent GH increase |
| Moderate appetite effect | Less ghrelin-mimetic hunger than GHRP-6 | More tolerable for patients not seeking appetite stimulation |
| Cortisol/prolactin | Moderate HPA axis activation | Less than GHRP-6 but more than ipamorelin |
| GH diagnostic | Standardized IV bolus test protocol | Approved diagnostic for GH deficiency in Japan |
| Synergy with GHRH | Enhanced GH release when combined with GHRH analogs | Common combination protocol in clinical use |
| Study | Design | Findings | Level |
|---|---|---|---|
| GH deficiency diagnosis | Japanese clinical validation | GHRP-2 stimulation test reliably differentiates GH-deficient from GH-sufficient subjects. Basis for Japanese regulatory approval. | Level I-II |
| GH release comparison | Clinical studies | GH release: GHRP-6 > GHRP-2 > ipamorelin. Selectivity: ipamorelin > GHRP-2 > GHRP-6. | Level II |
| Body composition | Clinical research | Improved lean mass and reduced fat mass in GH-deficient subjects over 12 weeks | Level II-III |
| Cortisol comparison | Clinical pharmacology | GHRP-2 increased cortisol ~40% less than GHRP-6 at equipotent GH-releasing doses | Level II |
Cortisol and prolactin elevation: Unlike ipamorelin, GHRP-2 produces measurable increases in cortisol and prolactin at standard doses. These elevations are typically transient and return to baseline within hours, but chronic use may warrant monitoring of these hormones.
Appetite stimulation: GHRP-2 increases appetite via ghrelin-receptor activation, though less intensely than GHRP-6. This can be beneficial for patients needing weight gain or recovery from illness, but problematic for those managing body weight.
Water retention and GH-related effects: As with all GH secretagogues, water retention, joint stiffness, and numbness/tingling may occur at higher doses.
Japanese regulatory data: GHRP-2's approval in Japan provides a level of regulatory validation uncommon among GH secretagogues. The diagnostic use approval required formal safety and pharmacokinetic studies in humans, providing a stronger safety data foundation than most non-approved peptides.
| Jurisdiction | Status |
|---|---|
| Japan | Approved as pralmorelin for GH deficiency diagnosis |
| FDA | Not approved |
| WADA | Banned under S2 |