GHRP-2 5mg – Premium Research Grade Growth Hormone Releasing Peptide

GHRP-2 (growth hormone-releasing peptide-2; international nonproprietary name pralmorelin) is a synthetic six-amino-acid peptide developed in the early 1990s by Cyril Bowers and colleagues at Tulane University as part of a structured medicinal-chemistry program to identify small peptides that release growth hormone from somatotropes by a mechanism distinct from growth hormone-releasing hormone (GHRH). The program produced a series of "growth hormone-releasing peptides" (GHRPs) — GHRP-1, GHRP-2, GHRP-6, and the related compound hexarelin — that share a common mechanism of action and that helped open the field that culminated in the 1999 identification of ghrelin as the endogenous ligand for the receptor at which these peptides act.

GHRP-2's sequence is D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2 (a six-residue peptide containing two non-proteinogenic amino acids that confer protease resistance and high receptor affinity). It binds and activates the growth hormone secretagogue receptor type 1a (GHSR-1a), the same receptor activated by endogenous ghrelin, and triggers release of growth hormone from anterior-pituitary somatotropes. GHRP-2 has been studied in published clinical-research contexts as a diagnostic agent for assessing GH-axis function, in particular for stimulation testing in suspected GH deficiency, and is approved for diagnostic use in Japan under the trade name Kaken.

This page is a research-only educational reference. GHRP-2 supplied as a research peptide is intended for laboratory and analytical work; no therapeutic or human-use claims are made on this page.

GHRP-2 is a synthetic hexapeptide secretagogue — a compound that stimulates the release of an endogenous hormone (in this case growth hormone) from its storage cells. It belongs to the family of growth hormone secretagogues (GHS), all of which act on the GHSR-1a receptor. Other members of the family include GHRP-1, GHRP-6, hexarelin, ipamorelin, and the orally bioavailable small-molecule MK-677 (ibutamoren).

The mechanism of GH release by GHRP-2 differs from GHRH in important ways. GHRH binds the GHRH receptor (a class B GPCR) on somatotropes and activates Gs/cAMP signaling. GHRP-2 binds the GHSR-1a receptor (a class A GPCR) on the same cells and activates Gq/IP3/calcium signaling. The two pathways converge to release stored GH but are pharmacologically distinct, and combining a GHRH analog (such as sermorelin, CJC-1295, or tesamorelin) with a GHS (such as GHRP-2 or ipamorelin) produces synergistic GH release that exceeds the effect of either alone. This synergy is the mechanistic rationale for the GHRH-plus-GHS combination protocols extensively studied in the GH secretagogue research literature.

GHRP-2 also has a documented effect on ACTH and cortisol release at higher doses, consistent with the broader pharmacology of the GHSR-1a receptor and ghrelin signaling. This off-target endocrine effect is one of the distinguishing features of GHRP-2 versus the more selective secretagogue ipamorelin, which causes much less ACTH/cortisol elevation in published research. GHRP-2 also increases prolactin to a modest extent in some research contexts.

It is important to be clear about what GHRP-2 is not. It is not GH itself — GHRP-2 stimulates release of endogenous GH from the somatotrope storage pool rather than supplying exogenous GH. It is not an approved therapy for adult or pediatric GH replacement in major Western jurisdictions; it is approved as a diagnostic stimulation agent in Japan. And it is not a "weight-loss drug" or anabolic agent in the lay sense; its pharmacology is GH-axis stimulation, with downstream effects depending on the integrated activity of GHRH, somatostatin, ghrelin, and IGF-1 feedback in the individual research model.

The growth-hormone-releasing-peptide story begins in the early 1980s in the laboratory of Cyril Bowers at Tulane, who observed that certain met-enkephalin analogs released GH from rat pituitary cultures by a mechanism distinct from GHRH. The original lead compound was GHRP-6, a hexapeptide that became the prototype for the class. Through structure-activity-relationship work in collaboration with medicinal chemists at the National Institutes of Health and several pharmaceutical companies, the Bowers group refined the chemistry to produce GHRP-1, GHRP-2 (more potent than the earlier compounds), and the structurally distinct hexarelin in the late 1980s and early 1990s.

Throughout this period the receptor for the GHRPs was unknown — the compounds were known to act on a receptor distinct from the GHRH receptor, and the receptor was provisionally called the growth hormone secretagogue receptor (GHS-R). In 1996, Howard and colleagues at Merck cloned the GHS-R from human and rat pituitary using expression-cloning methodology, identifying the receptor (renamed GHSR-1a) as a Gq-coupled class A GPCR. The endogenous ligand for the receptor remained unknown until 1999, when Kojima, Kangawa and colleagues in Japan reported the isolation and characterization of ghrelin, a 28-amino-acid acylated peptide produced primarily by stomach X/A-like cells, as the endogenous GHSR-1a agonist. That discovery retrospectively placed the entire GHRP series — including GHRP-2 — as synthetic ghrelin-receptor agonists.

In parallel with this basic-science arc, GHRP-2 was developed for clinical-research use as a GH-stimulation diagnostic. The IV-administered peptide produces a reliable, dose-dependent GH peak that can be used for stimulation testing in suspected GH deficiency in pediatric and adult populations. It is approved in Japan for this diagnostic indication. Several Western pharmaceutical companies (including Wyeth and others) conducted clinical-research programs around GHRP-2 and related compounds in the 1990s and 2000s, including investigation in adult GH deficiency, but no GHS has been approved as a GH replacement therapy in major Western jurisdictions.

The broader ghrelin-receptor field has continued to evolve. The orally bioavailable small-molecule MK-677 (ibutamoren) was developed by Merck in the late 1990s and has been studied extensively in published research. The Pfizer compound macimorelin (Aeterna Zentaris originated, now branded as Macrilen/Ghryvelin) was approved by the US FDA in 2017 as a diagnostic stimulation agent for adult GH deficiency — establishing a Western regulatory precedent for the ghrelin-receptor-agonist diagnostic class.

The GHSR-1a receptor is a Gq-coupled seven-transmembrane GPCR with unusual pharmacology. It exhibits high constitutive (ligand-independent) activity — in published studies in heterologous expression systems and in native tissues, the receptor signals at roughly 50% of its maximum activity in the absence of ligand. Ghrelin and synthetic GHRPs further increase the activity to full agonism; inverse agonists (in research only) suppress the constitutive activity. This unusual constitutive activity has been a major topic in ghrelin-receptor pharmacology research and is relevant to interpreting receptor occupancy and signaling assays.

In the anterior pituitary, GHSR-1a is expressed on somatotropes — the GH-producing cells. Activation by GHRP-2 triggers Gq/phospholipase-C/IP3 signaling, calcium mobilization from intracellular stores, and exocytosis of stored GH-containing secretory granules. This Gq-driven GH release mechanism is mechanistically distinct from, and synergistic with, GHRH-driven Gs/cAMP/PKA signaling at the same cells. The two pathways combine multiplicatively rather than additively in many published research models, which is the mechanistic basis for GHRH-plus-GHRP combination research protocols.

Beyond the somatotrope, GHSR-1a is expressed in the hypothalamus (arcuate nucleus NPY/AgRP neurons and other populations), in the brainstem, in the vagal afferent system, and in various peripheral tissues including the gastrointestinal tract, pancreas, and cardiovascular system. Ghrelin signaling in these tissues mediates the broader endocrine and metabolic effects associated with ghrelin biology: appetite stimulation (via arcuate AgRP/NPY activation), gastric motility, pancreatic islet effects, and cardiovascular effects. GHRP-2 administration in research models replicates many of these effects to varying degrees.

The downstream consequences of GHRP-2-induced GH release are mediated by GH itself and by IGF-1, the principal downstream effector of GH at the liver. GH released from the pituitary engages the GH receptor (GHR), activates JAK2/STAT5 signaling, and drives hepatic IGF-1 transcription as well as direct GH effects in adipose, muscle, and other tissues. IGF-1 then feeds back negatively on both GH release and somatotrope sensitivity, providing the homeostatic regulation that prevents runaway GH activity.

In published clinical-research diagnostic use, IV GHRP-2 produces a reproducible GH peak typically within 15-30 minutes of administration, with a return to baseline over the following hour. The peak GH response is interpreted in the context of patient body composition, age, sex, and IGF-1 status. The peptide is rapidly cleared, with a short plasma half-life consistent with its protease-resistant but otherwise small-peptide pharmacokinetics.

GHRP-2 is a synthetic hexapeptide with the sequence D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2 (C-terminally amidated). The molecular formula is C45H55N9O6 and the molecular weight is approximately 817.9 g/mol. The peptide contains two non-proteinogenic amino acids — D-2-naphthylalanine at position 2 and D-phenylalanine at position 5 — that confer protease resistance and contribute to the binding interaction with the GHSR-1a receptor. The C-terminal amidation further protects the molecule from carboxypeptidase degradation.

Research-grade GHRP-2 is produced by standard solid-phase peptide synthesis (SPPS), typically using Fmoc-chemistry on Rink amide resin to install the C-terminal amide. The crude product is purified by reversed-phase HPLC to ≥98% purity for research use and verified by analytical HPLC and mass spectrometry. The peptide is supplied as a lyophilized white powder, typically as the acetate salt, and is reconstituted in sterile bacteriostatic water or sterile saline for laboratory use. It is stable at -20 °C or below in the lyophilized state and at 4 °C for short-term use after reconstitution.

In published GH-axis research, GHRP-2 is used as a tool reagent and as a clinical-research diagnostic. The principal applications include:

GH stimulation testing. The reliable, dose-dependent GH release elicited by IV GHRP-2 makes it useful as a stimulation agent in research-protocol assessment of pituitary somatotrope reserve. In Japan it is approved for this diagnostic indication. In Western research, comparable protocols have been published using GHRP-2 alone or in combination with GHRH.

GHRH-plus-GHRP synergy studies. The combination of GHRH (or a GHRH analog such as sermorelin or CJC-1295) with GHRP-2 produces a markedly larger GH peak than either alone. This synergy has been characterized in published research as a tool for probing the maximal somatotrope GH reserve.

Ghrelin pharmacology research. Because GHRP-2 is a high-affinity GHSR-1a agonist with simpler pharmacology than the full 28-residue acylated ghrelin, it is used as a reference agonist in receptor binding assays, signaling assays, and selectivity studies.

Comparative studies versus ipamorelin and other GHS. The differential selectivity profile — GHRP-2 has documented ACTH/cortisol/prolactin effects, ipamorelin much less — makes the comparison a useful tool for dissecting GHSR-1a-mediated versus off-target effects.

Animal-model muscle, body-composition, and metabolic research. In rodent and canine research models, GHRP-2 has been used to investigate GH-axis stimulation effects on body composition, IGF-1, glucose metabolism, and related endpoints. Effects in these models depend on dose, duration, route, species, and the integrated activity of feedback loops.

All applications are research-context. Nothing on this page describes a clinical protocol, dose, or therapy for human use outside an approved diagnostic context.

GHRP-2 sits within a family of growth hormone secretagogues that share GHSR-1a agonism but differ in potency, selectivity, and pharmacokinetics.

GHRP-2 is a synthetic hexapeptide growth hormone secretagogue developed in the early 1990s by Cyril Bowers' laboratory at Tulane. It is a high-affinity agonist of the GHSR-1a receptor — the same receptor activated by endogenous ghrelin (identified in 1999) — and triggers Gq/PLC/IP3-mediated release of stored growth hormone from anterior-pituitary somatotropes. Its mechanism is pharmacologically distinct from, and synergistic with, GHRH-driven Gs/cAMP-mediated GH release, which is the rationale for GHRH-plus-GHRP combination research protocols.

GHRP-2 is approved in Japan as a diagnostic stimulation agent for GH-axis assessment. It is studied in published clinical-research and basic-science contexts as a tool reagent for somatotrope reserve testing, for comparative GHSR-1a agonist pharmacology versus ipamorelin and other secretagogues, and for ghrelin-receptor biology more broadly. Documented off-target effects on ACTH, cortisol, and prolactin distinguish it from the more selective ipamorelin.

This page is research educational only. GHRP-2 supplied as a research peptide is intended for laboratory and analytical work; no therapeutic or human-use claims are made.