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'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 elevation: Less than GHRP-6 but still present. Monitor with chronic use.
Prolactin increase: Moderate elevation. Less gynecomastia risk than GHRP-6 but not negligible.
Appetite stimulation: Present but milder than GHRP-6. Some users report moderate hunger increase.
Water retention: GH-mediated. Standard precautions as with all GH-elevating therapies.
| Jurisdiction | Status |
|---|---|
| Japan | Approved as pralmorelin for GH deficiency diagnosis |
| FDA | Not approved |
| WADA | Banned under S2 |