GHRP-2
Also known as: Pralmorelin · KP-102 · growth hormone releasing peptide 2
The reference growth-hormone-releasing peptide developed as a diagnostic and research tool for GH-axis characterisation, with well-established GH-releasing pharmacology and licensed diagnostic use in some jurisdictions.
GHRP-2 (pralmorelin) is the reference growth-hormone-releasing peptide with licensed diagnostic clinical use in Japan for GH-deficiency testing; intermediate selectivity profile.
Evidence tier: A — ≥1 RCT + meta-analysis or approved clinical use
- Category
- Sleep & Recovery
- Half-life
- Approximately 15-20 minutes plasma
Section 1
Overview
GHRP-2 (pralmorelin) is a synthetic hexapeptide growth-hormone-releasing peptide developed as the reference research and diagnostic tool for GH-axis characterisation. The compound is licensed in Japan (as pralmorelin) for GH-deficiency diagnostic testing, providing a licensed clinical use base that most GHRPs lack. Outside Japan, it functions as a research chemical widely used in GH-axis research applications.
In research-peptide practice, GHRP-2 provides the reference ghrelin-receptor arm signalling for GH-axis research protocols. Its GH-releasing potency is intermediate between the highly-selective Ipamorelin and the most-potent Hexarelin. Off-target effects on cortisol, prolactin, and ACTH release are more pronounced than for Ipamorelin but less than for Hexarelin — the intermediate profile that has motivated its continued use despite the availability of more selective alternatives.
The cognitive-relevance angle is indirect, following the same GH-axis sleep-cognition framework as the other GHRP-family compounds. Direct cognitive-endpoint clinical trials have not been completed, but the mechanism-of-action framework and licensed diagnostic clinical use provide a substantial acute-safety database for research applications.
Section 2
Discovery & History
- Developed as one of the first generation of synthetic ghrelin-receptor agonists for GH-axis research and diagnostic applications.
- Licensed in Japan (as pralmorelin) for GH-deficiency diagnostic testing, providing a licensed clinical use base and substantial acute-safety database from decades of diagnostic clinical use.
- Extensively characterised across the 1990s and 2000s for GH-axis pharmacology, appetite effects, and metabolic effects.
- Widely adopted in research-peptide practice as a reference ghrelin-receptor arm research tool.
- Superseded in some research applications by the more selective Ipamorelin, though GHRP-2 remains the reference GHRP for many research protocols.
Section 3
Mechanism of Action
- 1Ghrelin-receptor (GHSR-1a) agonism on pituitary somatotroph cells, driving GH release from the pituitary — the primary mechanism-of-action.
- 2Moderate off-target effects on cortisol, prolactin, and ACTH release — more pronounced than for Ipamorelin but less than for Hexarelin, providing the intermediate selectivity profile.
- 3Combined pulse-effect with GHRH analogues — GHRP-2 provides the ghrelin-receptor arm signalling that potentiates the GHRH-receptor arm signalling in stack research configurations.
- 4Systemic GH-mediated effects — increased IGF-1 production, downstream metabolic and tissue-repair effects, and CNS-relevant IGF-1 signalling.
- 5Sleep-onset GH pulse augmentation — the indirect cognitive-relevance mechanism via sleep-mediated memory consolidation.
- 6Central ghrelin-receptor effects on appetite regulation via hypothalamic ghrelin-receptor engagement — the appetite-stimulating pharmacology that GHRP-2 shares with the other GHRPs.
- 7Reported effects on body composition (lean mass, adiposity) via the systemic GH mechanism.
Section 4
Researched Benefits
Findings reported in the published preclinical and clinical literature. Effects in research contexts do not constitute claims of therapeutic benefit in humans.
- 1Licensed diagnostic clinical use in Japan providing substantial acute-safety database — an unusual advantage for a GHRP-family compound.
- 2Reference GHRP for GH-axis research protocols with well-characterised pharmacology.
- 3Effective research-tool combination with GHRH analogues for physiological GH-pulse research.
- 4Intermediate selectivity profile between the highly-selective Ipamorelin and the most-potent Hexarelin.
- 5Reported effects on body composition, tissue-repair markers, and metabolic parameters in research applications.
- 6Sleep-onset GH pulse augmentation with indirect cognitive-relevance via sleep-mediated memory consolidation.
- 7Appetite-stimulating effects providing research applications in cachexia and appetite-regulation research contexts.
Section 5
Theoretical Dosing & Protocols
| Route | Dosage | Frequency | Duration |
|---|---|---|---|
| Subcutaneous injection (research and licensed diagnostic use) | 100-300 mcg per dose in research protocols; licensed diagnostic dose is 100 mcg IV bolus | 1-3× daily in research configurations | Diagnostic use is single-dose; research protocols continue 4-12 weeks in most contexts |
Note: The licensed diagnostic dose provides the reference for research-context dose selection.
Section 6
Administration Routes
- Subcutaneous injection — the primary research route.
- Intravenous administration — the licensed diagnostic route.
- Intramuscular administration in some research contexts.
- Oral administration is not viable — the peptide is degraded by gastrointestinal proteases.
Section 7
Safety Profile
Commonly reported
- · Well-tolerated in the licensed diagnostic clinical experience.
- · Injection-site reactions with subcutaneous administration.
- · Occasional headache during initial dosing.
- · Mild transient effects on cortisol and prolactin — the intermediate off-target profile.
- · Appetite stimulation — the expected ghrelin-receptor-mediated effect.
Rare / theoretical
- · Diabetes precipitation or worsening of glycaemic control in susceptible research subjects.
- · GH-mediated effects on cardiac hypertrophy in chronic high-dose research.
- · Theoretical GH-mediated tumour-growth concerns in active malignancy.
- · Rare hypersensitivity reactions.
- · Tolerance development to the GH-releasing effect with chronic use (intermediate between Ipamorelin and Hexarelin).
Contraindications
- · Not authorised for cognitive or GH-therapy indications in the UK.
- · Active malignancy — theoretical contraindication via the GH-axis mechanism.
- · Pregnancy and lactation.
- · Severe uncontrolled diabetes.
Section 8
UK & EU Regulatory Context
United Kingdom
Not a licensed medicine in the UK. Research chemical only.
European Union
Not approved by the EMA. Licensed as pralmorelin in Japan for GH-deficiency diagnostic testing.
Section 9
Clinical Studies Summary
GHRP-2 pharmacokinetics and GH-releasing profile
Foundational clinical pharmacology characterisation of GHRP-2's pharmacokinetic profile and GH-releasing effect time-course, establishing the reference pharmacology for the GHRP class and providing the mechanistic framework for the subsequent development of more selective analogues.
GHRP-2 in GH-deficiency diagnostic testing (Japan)
The licensed diagnostic clinical use programme in Japan providing the substantial acute-safety database from decades of clinical use and establishing the reference dose for GH-releasing effect. Pralmorelin remains the licensed diagnostic form in that jurisdiction.
GHRP-2 + GHRH combined GH-release research
Research characterising the combined-arm effect of GHRP-2 plus GHRH analogues on GH pulse magnitude, providing the reference GHRP-arm characterisation for the modern GH-axis stack research practice.
GHRP-2 appetite-stimulating effects and cachexia research
Clinical research applications of GHRP-2 in cachexia and appetite-regulation research contexts, demonstrating the appetite-stimulating effects via the central ghrelin-receptor mechanism. Provides the distinctive research application angle beyond the primary GH-axis research use.
Section 10
Frequently Asked Questions
Section 10a
Practical Research Guidance
Cycle guidance
Reconstitution & storage
UK sourcing notes
Section 11
Sourcing for Laboratory Research
Sourcing GHRP-2 for laboratory research
Researchers in the United Kingdom and elsewhere typically obtain GHRP-2 from specialist research-chemical suppliers. Purity, third-party testing, and supplier transparency are the principal differentiators worth evaluating before placing an order. The two suppliers below are commonly referenced in UK research contexts.
Reminder: research peptides are sold strictly for in vitro and preclinical laboratory purposes. Importation or supply for human consumption is not permitted under UK medicines legislation.