This data is for laboratory research purposes only. Not for human or animal consumption.
What is GHRP-2?
GHRP-2 (Growth Hormone-Releasing Peptide-2), also known by its INN name pralmorelin, is a synthetic hexapeptide growth hormone secretagogue (GHS) that acts on the ghrelin receptor (GHSR-1a) to stimulate pulsatile growth hormone (GH) release from anterior pituitary somatotroph cells. With a molecular formula of C₄₅H₅₅N₉O₆ and a molecular weight of approximately 818 g/mol, GHRP-2 is one of the most potent and well-characterized synthetic GHRPs in the published literature. It is not approved as a therapeutic drug in the United States; its clinical applications to date have been primarily diagnostic.
Mechanism of Action
GHRP-2 functions by binding to and activating the growth hormone secretagogue receptor type 1a (GHSR-1a), a G protein-coupled receptor expressed on anterior pituitary somatotroph cells, hypothalamic neurons, and peripheral tissues including the heart, adrenal glands, and liver. GHSR-1a activation triggers a Gαq/11-coupled phospholipase C signaling cascade, producing inositol triphosphate (IP₃) and diacylglycerol (DAG), which mobilize intracellular calcium stores and activate protein kinase C — together driving exocytosis of pre-formed GH secretory granules.
Unlike GHRH (growth hormone-releasing hormone), which acts through a distinct Gαs-coupled receptor on the same somatotroph cells, GHRP-2 bypasses hypothalamic regulation entirely, making it useful as a pharmacological probe for directly assessing pituitary GH reserve capacity independent of hypothalamic GHRH tone. When co-administered with GHRH, GHRP-2 produces synergistic GH release substantially greater than either stimulus alone — a pharmacodynamic property exploited in pituitary stimulation testing protocols.
GHRP-2 also demonstrates a secondary effect of cortisol and prolactin elevation not seen with selective GHRPs such as ipamorelin, owing to partial GHSR-1a activity at corticotroph and lactotroph cell populations. This is an important methodological consideration when selecting a GHS for research protocols where adrenal axis stimulation is undesirable.
GH Secretagogue Activity in Research
Preclinical and clinical research has characterized GHRP-2's GH-stimulating properties across multiple models:
- Dose-dependent GH secretion has been documented in rodent, primate, and human studies; doses in published research typically range from 1 µg/kg to 2 µg/kg IV, with peak plasma GH responses in the range of 20–50 ng/mL in healthy adult subjects
- Clinical diagnostic application: GHRP-2 stimulation testing has been used as a validated method for assessing GH secretory reserve in suspected GH deficiency, with published normative data from multiple centres
- Pituitary function benchmarking: In regenerative medicine research (Nishimoto et al., 2025, PMID 40277822), GHRP-2 stimulation testing in pituitary adenoma patients established maximal GH secretion capacity at 25.1 ng/mL average peak in subjects with intact somatotroph function — data intended to serve as transplantation benchmark values for hypothalamic-pituitary organoid research
Observed Laboratory Results (Anchor Study — PMID 40277822)
This study analyzed pituitary function data from 28 patients with pituitary adenomas, a proportion of whom had intact GH and ACTH secretory capacity. Key findings:
- Average peak GH response to GHRP-2 stimulation: 25.1 ng/mL (across 12 subjects with preserved GH secretion)
- ACTH comparison arm: average ACTH peak after CRH stimulation was 97.2 pg/mL (across 16 subjects with intact ACTH secretion)
- Research application: These maximal secretory capacity thresholds were established to guide safety parameters for adenohypophyseal cell transplantation in future regenerative medicine protocols
Comparison to Related GHRPs
GHRP-2 is frequently compared to two structurally related hexapeptides in the research literature:
- GHRP-6 (Growth Hormone-Releasing Peptide-6): Like GHRP-2, GHRP-6 is a GHSR-1a agonist hexapeptide, but differs structurally and demonstrates somewhat lower GH stimulation potency per molar unit in direct comparisons; GHRP-6 has a more extensively studied cardioprotective literature
- Ipamorelin: A pentapeptide GHSR-1a agonist with higher receptor selectivity and negligible cortisol/prolactin stimulation compared to GHRP-2; frequently selected in research protocols where isolated GH axis stimulation is needed without adrenal confounding
Research Context and Regulatory Status
GHRP-2 is not FDA-approved for any therapeutic indication. It is not scheduled as a controlled substance in the United States and has been available through 503A compounding pharmacies. Its primary research applications include pituitary GH reserve testing, GH deficiency diagnosis, and as a pharmacological tool in GH axis biology research. GHRP-2's GHSR-1a binding profile has also made it a reference compound in studies investigating the ghrelin receptor system's role in energy homeostasis, appetite regulation, and cardiac function.