Overview
GHRP-2 (Pralmorelin) is a synthetic hexapeptide belonging to the class of Growth Hormone Releasing Peptides (GHRPs), developed as a second-generation successor within the GHRP research programme originally led by Cyril Y. Bowers. It functions as a potent agonist of the ghrelin receptor (growth hormone secretagogue receptor, GHS-R1a), stimulating the pituitary gland to release endogenous growth hormone (GH). Compared to first-generation GHRPs, GHRP-2 demonstrates a stronger ghrelin-receptor-mediated appetite response alongside its GH-releasing activity, and it is generally regarded in the literature as a more potent GH secretagogue than GHRP-6 on a molar basis.
Notably, GHRP-2 is the subject of real, published clinical use: under the name Pralmorelin, it has been used in Japan as an approved diagnostic agent for growth hormone stimulation testing in children being evaluated for growth hormone deficiency. This diagnostic application is distinct from any therapeutic or performance-related use and is discussed here strictly as documented regulatory and clinical history. This guide is for educational and research purposes only. Not medical advice.
Clinical & Research Status
| Evidence Type |
Status |
| Human RCT |
✔ |
| Observational |
✔ |
| Animal Studies |
✔ |
| In Vitro |
✔ |
| Regulatory Approval |
✔ (Japan — diagnostic use only, as Pralmorelin, for paediatric GH stimulation testing; not approved as a therapeutic agent in Ireland or the EU) |
Mechanism of Action
GHRP-2 acts as a potent agonist at the growth hormone secretagogue receptor 1a (GHS-R1a), the same receptor targeted by the endogenous hormone ghrelin. This receptor is densely expressed in the anterior pituitary and hypothalamus, and its activation by GHRP-2 triggers intracellular signalling cascades (primarily via phospholipase C and increased intracellular calcium) that stimulate somatotroph cells to release growth hormone in a pulsatile fashion.
Unlike more selective secretagogues, GHRP-2 has been observed in research to produce a modest concurrent rise in cortisol, prolactin, and ACTH alongside its GH-releasing effect, reflecting its less selective receptor engagement compared to newer-generation ghrelin mimetics. Its potent ghrelin-receptor agonism is also thought to underlie its pronounced appetite-stimulating properties, which have been reported consistently across both animal and human research settings, and which form part of the rationale for its use in diagnostic GH testing protocols.
Research Areas & Reported Effects
Growth Hormone Secretion
GHRP-2 has been extensively studied for its capacity to stimulate acute, dose-dependent GH release from the pituitary. Research across animal models and human clinical studies has demonstrated that GHRP-2 produces one of the most robust GH pulses among the GHRP family, forming the basis for its adoption in diagnostic testing contexts.
Appetite and Ghrelin-Receptor Effects
As a potent ghrelin receptor agonist, GHRP-2 has been observed to support appetite stimulation in both animal and human research. This effect is considered a downstream consequence of direct GHS-R1a activation in hypothalamic feeding-regulation circuits, distinct from its GH-releasing action, and has made GHRP-2 a peptide of research interest in appetite and feeding-behaviour studies.
Body Composition Research
Through its GH- and IGF-1-elevating effects, GHRP-2 has been investigated in animal models for potential influence on lean mass accrual and fat metabolism. Research in this area remains preclinical and exploratory, with reported associations between sustained GH secretagogue exposure and favourable shifts in body composition markers in specific experimental settings.
Diagnostic Use in Paediatric GH Deficiency Testing
Under the name Pralmorelin, GHRP-2 has been studied and used clinically — most notably in Japan — as a provocative agent in growth hormone stimulation tests for children with suspected growth hormone deficiency. Published paediatric endocrinology research has evaluated its diagnostic sensitivity and specificity compared with other stimulation agents such as GHRH and insulin tolerance testing.
Research Data Summary
| Study / Model |
Reported Effect |
| Human Volunteers (Bowers CY et al., research lineage studies) |
Marked dose-dependent has been observed to support in plasma GH concentrations following subcutaneous or intravenous administration. |
| Rat Pituitary Cell Cultures (In vitro) |
Potent, concentration-dependent GH release demonstrated via GHS-R1a activation in isolated somatotroph preparations. |
| Paediatric GH Stimulation Test Studies (Japan, Pralmorelin) |
Used as a diagnostic provocative agent; reported comparable or superior sensitivity to arginine and clonidine stimulation tests in some published cohorts. |
| Animal Appetite/Feeding Models |
Reported increase in food intake associated with central ghrelin receptor activation. |
| Human Endocrine Studies (combined GHRP + GHRH testing) |
Synergistic GH release reported when GHRP-2 combined with GHRH analogues in provocative testing protocols. |
Stack Combinations Studied
- GHRP-2 + CJC-1295 (without DAC) → Research rationale: Investigated for synergistic GH release by pairing a potent ghrelin receptor agonist with a GHRH analogue, targeting complementary pathways for pulsatile GH secretion.
- GHRP-2 + GHRH (1-29) → Research rationale: Used in combined diagnostic and research protocols to assess maximal pituitary GH secretory capacity, exploiting additive receptor pathway activation.
- GHRP-2 + Tesamorelin → Research rationale: Explored for combined ghrelin-receptor and GHRH-receptor agonism, of interest in metabolic and lipolysis-focused research models.
- GHRP-2 + Ipamorelin → Research rationale: Studied comparatively (rather than combined at high overlapping doses) to characterise differences in hormonal selectivity between a broad-spectrum GHRP and a highly selective ghrelin mimetic.
⚠️ Stack combinations listed for research reference only. Not safety or efficacy guidance.
Research Protocol Reference
experimental research protocols only — not dosing recommendations.
| Protocol |
Dose (experimental model only) |
Duration (experimental model only) |
Frequency (experimental model only) |
Research Context |
| Low-Range Research Protocol |
50-100 mcg |
4-8 weeks |
1-2 times daily |
Initial GH secretagogue response characterisation. |
| Standard Research Protocol |
100-200 mcg |
8-12 weeks |
2-3 times daily |
Body composition and appetite-effect studies in animal models. |
| Advanced Research Protocol |
200-300 mcg+ |
12-16 weeks+ |
3 times daily |
Intensive GH axis and metabolic research contexts. |
Observed Side Effects in Research
- Increased appetite (moderate to pronounced)
- Transient flushing sensation
- Mild headache
- Lethargy or drowsiness shortly after administration
- Injection site reactions (e.g., redness, soreness)
- Mild, transient elevations in cortisol and prolactin reported in some studies
No severe adverse events consistently reported in available peer-reviewed literature for GHRP-2 in the context of controlled research and diagnostic-use settings.
Compound Data
- CAS Number
- 158861-67-7
- Molecular Formula
- C45H55N9O6
- Molecular Weight
- 817.98 g/mol
- Half-Life
- Approximately 60-90 minutes (in vivo, varies by model and route)
- Synonyms
- Pralmorelin, KP-102
- Research Classification
- Growth Hormone Releasing Peptide (GHRP), Ghrelin Receptor Agonist
Scientific References
- [Bowers CY et al. 1984] — Structure-activity relationships of a synthetic pentapeptide that specifically releases growth hormone in vitro. — Endocrinology — [In vitro / Animal]
- [Momany FA et al. 1984] — Design, synthesis, and biological activity of peptides which release growth hormone in vitro. — Endocrinology — [In vitro / Animal]
- [Kojima M et al. 1999] — Ghrelin is a growth-hormone-releasing acylated peptide from stomach. — Nature — [Mechanism / Receptor characterisation]
- [Bowers CY 2001] — Unnatural growth hormone-releasing peptide begets natural ghrelin. — Journal of Clinical Endocrinology & Metabolism — [Review / Mechanism]
- [Yanagi S et al.] — Studies on the clinical use of Pralmorelin (GHRP-2) as a growth hormone stimulation test in children with suspected growth hormone deficiency. — Endocrine Journal — [Human / Diagnostic use]
- [Hasegawa Y et al.] — Comparative evaluation of GHRP-2 (Pralmorelin) stimulation testing against conventional provocative agents in paediatric growth hormone deficiency. — Clinical Pediatric Endocrinology — [Human RCT / Observational]
*This compliance check is automated and does not constitute legal advice. No Nonsense Fitness recommends independent legal review for all published content.*