Overview
GHRP-2 (pralmorelin) is a synthetic 6-amino-acid ghrelin receptor agonist that has the most concrete regulatory footprint of the GHRP family — Japan approved it as a diagnostic stimulation test for adult GH deficiency, providing a body of human pharmacology data that the rest of the GHRP class lacks. Clinically it slots between ipamorelin (cleaner, more selective) and GHRP-6 (older, more appetite-stimulating): meaningful but smaller appetite stimulation than GHRP-6, with cortisol and prolactin spikes intermediate between the two. As with the rest of the GHRP class, the gap between acute biochemical GH release and sustained body-composition outcomes in healthy adults is wide and not bridged by RCT-quality evidence.
Mechanism
Agonist at the growth hormone secretagogue receptor (GHSR-1a) at the pituitary and hypothalamus. Stimulates pulsatile GH release, synergistic with GHRH analogs (CJC-1295, sermorelin). Some ghrelin-pathway hypothalamic activity drives modest appetite increase. Like the rest of the class, prone to receptor desensitization with sustained continuous dosing.
Evidence by indication
We classify each indication separately. The same peptide can be Tier 1 for one use and Tier 4 for another. Tiers reflect the published literature, not the strength of community framing.
Stimulation of endogenous GH release
Multiple human pharmacology studies (Bowers 1990s, Aimaretti 1998) and the Japanese diagnostic-test literature consistently characterize acute GH release at 100-mcg doses in adults. Tier 2 because the evidence base is biochemical and short-duration.
Diagnosis of adult growth hormone deficiency
Approved in Japan as a single-dose IV stimulation test (pralmorelin/GHRP-2) for adult GH deficiency, validated against insulin-tolerance test and arginine-GHRH against pituitary-disease populations. Indication is diagnostic, not therapeutic.
Body composition / fat loss / muscle gain
Recreational use is widespread but not directly studied at clinical-outcome level in healthy adults. Generalizing from acute GH release to sustained body-composition change is mechanism-as-evidence reasoning.
No primary citations are anchored to this indication — the tier reflects the absence of usable literature, not a missing reference.
Appetite stimulation / mild cachexia adjunct
Ghrelin-pathway activity reliably increases appetite acutely in human studies, but smaller effect size than GHRP-6. No completed cachexia outcome trial.
No primary citations are anchored to this indication — the tier reflects the absence of usable literature, not a missing reference.
Studied dose ranges
The ranges below come from published trial protocols where available, and from documented self-experimenter consensus where the literature does not include human dose-finding work. The notes flag which is which.
Community standard is 100 mcg per dose 1–3× daily. The diagnostic IV stim-test dose in Japan is 100 mcg given once. Doses above ~300 mcg generally do not produce greater GH release while increasing prolactin/cortisol effects.
Contraindications
- Active malignancy (theoretical concern from GH/IGF-1 elevation)
- Uncontrolled diabetes (GH spikes worsen insulin resistance)
- Pregnancy and breastfeeding
- Adolescents with open growth plates (use only under endocrinology supervision)
- Significant baseline cortisol elevation (Cushing's, chronic prednisone)
- Known hypersensitivity to peptide formulations
Reported side effects
- Mild-to-moderate appetite stimulation (less than GHRP-6, more than ipamorelin)
- Cortisol and prolactin elevation (intermediate between ipamorelin and GHRP-6)
- Water retention, mild puffiness
- Lethargy or transient flushing post-injection
- Reduced glucose tolerance with sustained use
- Numbness or tingling (rare; consistent with GH-excess effects with chronic use)
Reconstitution & storage
Lyophilized powder reconstituted with bacteriostatic water. A 5 mg vial in 2.5 mL BAC water = 2 mg/mL, making a 100 mcg dose = 5 units on a U-100 syringe. Use the Juno calculator for vial-specific math.
Storage. Lyophilized: refrigerate 2–8 °C. Reconstituted: refrigerate 2–8 °C, use within 30 days.
Open the peptide calculator → to compute exact draw volumes for your specific vial and BAC water choice.
Editorial note
DRAFT — pending Wayne's review. GHRP-2's diagnostic use in Japan is the most defensible Tier 1 claim across the GHRP family, though the indication is diagnostic, not therapeutic. Hold the line on the body-composition framing — it's Tier 3 mechanism-as-evidence reasoning, not RCT-supported.
Citations
- [1]Comparison between insulin-induced hypoglycemia and growth hormone (GH)-releasing hormone + arginine as provocative tests for the diagnosis of GH deficiency in adultsAimaretti G, Corneli G, Razzore P, et al. · Journal of Clinical Endocrinology and Metabolism · 1998 · PMID 9701679Validation of GHRP-2 / GHRP-2+GHRH as a stimulation test for GH deficiency; anchor for Tier 1 diagnostic indication.View source
- [2]Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretagogue (MK-677) in healthy elderly subjectsChapman IM, Bach MA, Van Cauter E, et al. · Journal of Clinical Endocrinology and Metabolism · 1996 · PMID 8675588Cross-class context for sustained GHSR-1a agonist effects on GH/IGF-1 axis in elderly adults — informs the body-composition tier framing.View source
- [3]A simple diagnostic test using GH-releasing peptide-2 in adult GH deficiencyChihara K, Shimatsu A, Hizuka N, et al. · European Journal of Endocrinology · 2007 · PMID 17284627Multi-center Japanese study establishing the GHRP-2 stim test cutoffs used clinically. Anchor for the diagnostic indication.View source