GHRP-2 is a research compound studied for its role in performance & hormone research. This page covers mechanism of action, published studies, preclinical protocols, and analytical specifications.
Quick Reference: GHRP-2
CAS Number
158861-67-7
Molecular Formula
C45H55N9O6
Molecular Weight
817.9 g/mol
Sequence / Structure
D-Ala-D-β-Nal-Ala-Trp-D-Phe-Lys-NH2 (hexapeptide)
Physical Form
Lyophilized powder
Purity (QSC)
≥99%
Storage
Store lyophilized at -20°C. Reconstituted: 4°C, use within 28 days.
Reconstitution
Add 2ml bacteriostatic water per vial. Swirl gently to dissolve.
Mechanism of Action
GHRP-2 (Pralmorelin) is a synthetic hexapeptide and ghrelin receptor (GHSR-1a) agonist developed as part of the original GH secretagogue research programme that ultimately produced ipamorelin. It is a second-generation GHRP — more potent than GHRP-6 but less selective than ipamorelin.
GHSR-1a Activation: GHRP-2 binds the ghrelin receptor with high affinity, activating intracellular phospholipase C (PLC) via Gq-protein coupling. PLC cleaves PIP2 into IP3 and DAG, raising intracellular calcium and activating PKC. This calcium-dependent mechanism is distinct from the cAMP pathway activated by GHRH, which explains the synergistic GH release observed when GHRP-2 is combined with GHRH analogs — they act through different second messenger cascades converging on GH granule exocytosis.
Selectivity Profile — The Key Research Distinction: Unlike ipamorelin, GHRP-2 produces moderate co-stimulation of cortisol and prolactin alongside GH release. This occurs because GHRP-2 has lower selectivity for GHSR-1a vs other pituitary receptors, and because GHSR-1a activation at higher doses stimulates CRH (corticotropin-releasing hormone) release, which in turn elevates ACTH and cortisol. This HPA axis co-activation is a confound in some research designs but is itself the study endpoint in others.
Appetite Stimulation: GHRP-2 produces mild appetite stimulation through hypothalamic ghrelin receptor activation — less pronounced than GHRP-6 but more than ipamorelin. This orexigenic effect is important context for research designs measuring food intake or body weight as endpoints.
Research Applications
GHSR Pharmacology: GHRP-2 is used to characterise GHSR-1a binding affinity, receptor occupancy, and signalling kinetics alongside ipamorelin and GHRP-6 in comparative receptor pharmacology studies.
GH/Cortisol Interaction Research: Because GHRP-2 elevates both GH and cortisol, it is used in research specifically examining the relationship between GH secretagogue administration, HPA axis activation, and the opposing anabolic (GH) vs catabolic (cortisol) hormonal environment.
Selectivity Comparison Studies: The GHRP-2 vs ipamorelin comparison is standard in GH secretagogue selectivity research — GHRP-2 represents the intermediate-selectivity reference point between the non-selective GHRP-6 and the highly selective ipamorelin.
Cardiac Research: GHRP-2 has been studied for direct cardioprotective effects in ischemia-reperfusion models, operating through GHSR-independent mechanisms including CD36 receptor activation — a research application distinct from its GH-releasing role.
Key Published Research
Primary publications relevant to GHRP-2 research. Full citations available via PubMed. QSC does not endorse or make claims based on this research.
Deghenghi et al. (1994)
“GH-Releasing Activity of Hexarelin, a New Growth Hormone Releasing Peptide” — Life Sciences
Establishes the GHRP-2 class pharmacology, receptor binding, and comparative potency vs other GHRPs in the original characterisation series.
Arvat et al. (1997)
“GHRP-2: Effects on GH, Cortisol, ACTH and Prolactin Secretion” — Journal of Clinical Endocrinology & Metabolism
Characterises GHRP-2’s selectivity profile in humans, documenting the GH/cortisol/prolactin co-stimulation pattern that distinguishes it from ipamorelin.
Broglio et al. (2002)
“Non-acylated Ghrelin Counteracts the Metabolic but Not Neuroendocrine Response to Acylated Ghrelin” — Journal of Clinical Endocrinology & Metabolism
Contextualises GHRP-2 within ghrelin receptor biology, relevant to research distinguishing acylated vs non-acylated ghrelin effects.
Research Protocol Reference
Model / Context
Dose Range
Route
Protocol Notes
Rodent GH/Cortisol Study
50–300 μg/kg
Intravenous or subcutaneous
Acute single-dose; serial sampling for GH, cortisol, ACTH at 15, 30, 60, 120 min
Selectivity Comparison
100 μg/kg GHRP-2 vs 100 μg/kg ipamorelin
Subcutaneous injection
Parallel group design; endpoint: GH, cortisol, prolactin AUC comparison
In Vitro GHSR Binding
0.001–1000 nM
Added to receptor binding assay
Competitive radioligand binding and cAMP/Ca2+ signalling assays
Frequently Asked Questions
What is GHRP-2?
GHRP-2 (Pralmorelin) is a synthetic hexapeptide GHSR-1a agonist that stimulates GH release from the pituitary alongside moderate cortisol and prolactin co-stimulation. It is used in GH secretagogue pharmacology research and as a selectivity comparison reference vs the more selective ipamorelin.
What is the difference between GHRP-2 and ipamorelin?
Both are GHSR-1a agonists producing GH release, but differ in selectivity. Ipamorelin produces GH release with negligible cortisol or prolactin co-stimulation. GHRP-2 produces moderate cortisol and prolactin elevation alongside GH — a meaningful confound in body composition research but useful in studies specifically examining HPA axis interactions.
Is GHRP-2 stronger than ipamorelin?
GHRP-2 produces somewhat higher peak GH release at equivalent doses, but at the cost of cortisol co-stimulation. For research requiring isolated GH axis effects, ipamorelin’s selectivity makes it the superior tool. For research studying GH secretagogue/HPA axis interactions, GHRP-2 is appropriate.
How should GHRP-2 be stored?
Lyophilized at -20°C. Reconstituted with bacteriostatic water: 4°C, use within 28 days.
What purity is QSC GHRP-2?
≥99% by HPLC and mass spectrometry. COA on product page, Janoshik-verified.
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