Overview
GHRP-2 (pralmorelin) is a synthetic hexapeptide that acts as a potent agonist of the ghrelin/GHS-R1a receptor. It is the second generation of GHRPs developed after GHRP-6, retaining the GH-releasing potency while reducing the strong appetite stimulation that characterizes GHRP-6. Unlike ipamorelin, GHRP-2 does produce modest increases in cortisol and prolactin alongside GH release. GHRP-2 has been studied in human clinical trials for growth hormone deficiency diagnosis (as a GH stimulation test agent) and in research protocols for body composition. It is more potent than GHRP-6 on a per-microgram basis for GH release.
Mechanism
GHRP-2 binds to GHS-R1a on pituitary somatotrophs and hypothalamic neurons, activating the same ghrelin receptor pathway as ipamorelin and hexarelin. It stimulates GH secretion via the phospholipase C/IP3 pathway and has a synergistic effect when combined with GHRH analogs (CJC-1295, sermorelin). The modest cortisol and prolactin elevation distinguishes it from the more selective ipamorelin.
Research Areas
Side Effects (Preclinical)
- – Transient cortisol and prolactin elevation
- – Flushing and warmth
- – Water retention
- – Increased appetite (less than GHRP-6)
Cautions
- – For research use only
- – Cortisol stimulation not ideal for subjects with adrenal or HPA axis sensitivity
- – Prolactin elevation may be relevant in breast cancer research contexts
What the research shows
GHRP-2 is approved in Japan as a diagnostic agent (pralmorelin, Ghrelin test) for GH deficiency, giving it one of the more robust safety profiles in the GHRP class with documented human pharmacokinetic data. Studies show it produces GH pulses of 20–40 ng/mL peak concentration in healthy subjects — comparable to the insulintolerance test (gold standard for GH deficiency diagnosis) but with a safer risk profile.
References
- Growth hormone releasing peptides and their analogs — Bowers CY et al. (1998)
- Pralmorelin (GHRP-2) as a diagnostic test for adult growth hormone deficiency — Kato Y et al. (2010)