GHRP-2 — Research Overview
Chemical Name: Growth Hormone-Releasing Peptide-2 (GHRP-2) International Nonproprietary Name: Pralmorelin Also Known As: GHRP-2, pralmorelin, pralmorelin hydrochloride, KP-102, GPA-748 Amino Acid Sequence: D-Ala-D-(β-naphthyl)-Ala-Ala-Trp-D-Phe-Lys-NH2 Structure: Synthetic hexapeptide (6 amino acids) — an analog of met-enkephalin engineered for potent GHS-R1a agonist activity. Contains D-amino acids at positions 1, 2, and 4 for proteolytic resistance. Molecular Weight: 817.97 daltons Regulatory Status: Approved in Japan as GHRP Kaken 100 (marketed by Kaken Pharmaceutical) for the diagnostic assessment of growth hormone deficiency — making GHRP-2 the only GHS-R1a agonist peptide to hold regulatory approval in any jurisdiction. Not approved by the FDA. WADA Status: Prohibited substance under S2 (peptide hormones, growth factors, related substances, and mimetics) Historical Context: Developed as one of a series of synthetic GH-releasing peptides by Cyril Bowers and colleagues, building on the observation that chemical analogs of met-enkephalin showed GH-releasing activity in pituitary cell cultures. GHRP-6 was identified first, followed by GHRP-1 (a heptapeptide), and then GHRP-2 and hexarelin as more potent hexapeptide analogs. Category: Synthetic GHS-R1a agonist / ghrelin mimetic / growth hormone secretagogue / neuroendocrine research peptide
Research Use Only — Disclaimer
The scientific literature on this page is provided strictly for educational and informational purposes. All Rogue Compounds products are intended for in-vitro laboratory research use only and are not approved by the FDA for human or animal consumption outside of any approved indications. The studies referenced below are independent third-party peer-reviewed publications. Rogue Compounds makes no claims that any product diagnoses, treats, cures, or prevents any disease or condition. Researchers are responsible for compliance with all applicable local, state, and federal regulations.
What Is GHRP-2?
GHRP-2 (pralmorelin) is a synthetic hexapeptide growth hormone secretagogue developed as part of the GHRP family of met-enkephalin analogs that preceded the discovery of ghrelin — the endogenous hormone that was later identified as the natural ligand for the receptor these compounds target. GHRP-2 is the most extensively clinically characterized member of the GHRP class, holding regulatory approval in Japan for diagnostic use in growth hormone deficiency assessment and having been studied across multiple published human clinical trials in the United States and Europe.
GHRP-2 is distinguished from other members of the GHRP class by its potency profile. In human subjects it consistently produces GH responses that exceed those generated by maximal effective doses of GHRH, making it a more potent acute GH secretagogue than the endogenous GHRH receptor pathway when used as a standalone agent. This potency, combined with its oral bioavailability (an unusual property for a peptide), its established clinical safety record from Japanese regulatory approval, and its utility as a pharmacological research tool for investigating GHS-R1a receptor biology and hypothalamic-pituitary axis function, has made it one of the most widely studied compounds in the GHS literature.
Unlike ipamorelin — the selective GHS-R1a agonist that elevates GH without affecting cortisol, ACTH, or prolactin — GHRP-2 is not fully selective for GH release. At GH-releasing doses, GHRP-2 also produces meaningful elevations in ACTH, cortisol, and prolactin. This broader hormonal profile distinguishes GHRP-2 from ipamorelin and is important for researchers designing experimental protocols.
The GHRP Family in Context
GHRP-2 belongs to a family of synthetic peptides discovered before the endogenous ghrelin system was characterized, which makes it a historically significant compound in neuroendocrinology. The sequence of discovery was as follows:
Cyril Bowers and colleagues in the 1970s observed that met-enkephalin analogs stimulated GH release from pituitary cultures. Systematic modification of this structure led to GHRP-6 as the first member of the family studied in depth, followed by GHRP-1, GHRP-2, and hexarelin. When ghrelin was isolated from the stomach in 1999 and its receptor (GHS-R1a) was characterized as the target these synthetic compounds had been activating for two decades, the entire GHRP class was recognized as pharmacological precedents of ghrelin itself.
This history means that GHRP-2 research spans from early 1980s pituitary cell culture work through 1990s human clinical trials and into contemporary research on ghrelin receptor biology, critical illness neuroendocrinology, and cardioprotection — a research arc of more than four decades with human data at multiple points.
Mechanism of Action
GHS-R1a agonism and GH release: GHRP-2 binds with high affinity to the growth hormone secretagogue receptor 1a (GHS-R1a), a G-protein coupled receptor expressed in the anterior pituitary gland on somatotroph cells and in the hypothalamus. GHS-R1a activation by GHRP-2 initiates a calcium-dependent intracellular signaling cascade through phospholipase C, driving GH synthesis and release from pituitary somatotrophs. This pathway is mechanistically distinct from the GHRH receptor (GHRHR) pathway — which operates through cAMP/PKA signaling — allowing the two receptor systems to produce synergistic GH responses when both are simultaneously activated.
Dual hypothalamic and pituitary action: In vivo, GHRP-2’s GH-releasing effects require an intact hypothalamic-pituitary connection. GHRP-2 acts both directly on pituitary somatotrophs and indirectly through the hypothalamus — increasing GHRH release and suppressing somatostatin tone from the periventricular nucleus — explaining why its in vivo GH response exceeds what direct pituitary action alone would predict.
GHRH+GHRP-2 synergy: The combination of GHRH (or GHRH analogs such as CJC-1295) with GHRP-2 produces GH responses substantially greater than either agent alone — a documented synergistic effect that has been quantified across multiple published human studies. In critical illness research, GHRH+GHRP-2 combined produced 2.5-fold greater GH responses than GHRP-2 alone, while the GHRP-2 alone response was itself more than fourfold greater than GHRH alone. This dual-receptor synergy is mechanistically explained by GHRP-2 activating the GHS-R1a pathway while GHRH activates the distinct GHRHR pathway — complementary rather than redundant stimulation of the same target somatotroph cells.
Multi-hormone effects — HPA and prolactin: Beyond GH release, GHRP-2 at GH-releasing doses elevates ACTH and cortisol through a hypothalamic mechanism involving arginine vasopressin (AVP) release, and elevates prolactin to a lesser degree. Published human data established that GHRP-2’s ACTH/cortisol-releasing activity is quantitatively similar to that of human corticotropin-releasing hormone (hCRH), while its prolactin-releasing activity is lower than that of TRH. This multi-hormone profile distinguishes GHRP-2 from the more selective ipamorelin and is relevant for researchers studying HPA axis interactions.
Orexigenic effects: GHRP-2 produces appetite stimulation through GHS-R1a activation in the hypothalamic arcuate nucleus, which is the same mechanism by which endogenous ghrelin drives meal initiation. The appetite-stimulating effect of GHRP-2 is less pronounced than that of GHRP-6 but is meaningfully present and has been confirmed in published human studies — making GHRP-2 a useful pharmacological research tool for studying ghrelin’s role in energy homeostasis and feeding behavior.
Cytoprotective effects: Published research on the GHRP class including GHRP-2 has documented cardioprotective, cytoprotective, and anti-apoptotic properties that appear to operate through mechanisms partially independent of GH release, including direct GHS-R1a receptor activity on cardiomyocytes and other peripheral tissues that express this receptor. These cytoprotective properties of GHRPs represent a distinct research direction from their classical GH secretagogue activity.
Published Research
Study 1 — GHRP-2 vs GHRH: GH, ACTH, Cortisol, and Prolactin Responses in Humans
Authors: Arvat E, Di Vito L, Maccagno B, Broglio F, Boghen MF, Deghenghi R, Camanni F, Ghigo E (University of Turin) Year: 1997 Journal: Peptides PMID: 9285939 Full text: https://pubmed.ncbi.nlm.nih.gov/9285939/
This landmark comparative human study directly characterized the endocrine specificity profile of GHRP-2 (and hexarelin) versus GHRH, TRH, and human CRH across GH, prolactin, ACTH, and cortisol responses in 6 normal young adults and 6 elderly subjects.
In young adults, 1 microgram/kg IV GHRP-2 and hexarelin induced a similar, strong GH response that was statistically significantly higher than that produced by the maximal effective dose of GHRH (P less than 0.05). Higher doses of 2 micrograms/kg produced even greater GH responses — confirming GHRP-2 as more potent than GHRH for acute GH release in humans.
In elderly subjects, the GH responses to 2 micrograms/kg IV GHRP-2 and hexarelin were similar to each other and higher than GHRH alone (P less than 0.05) but lower than those in young subjects (P less than 0.01) — a clinically relevant age-related attenuation.
GHRP-2 elevated prolactin, ACTH, and cortisol in addition to GH, confirming it is not fully selective. The ACTH/cortisol response to GHRP-2 was quantitatively similar to the response to human CRH, while the prolactin response was lower than that of TRH.
The authors concluded that GHRP-2 activity is not fully specific, as it induces similar increases in PRL, ACTH, and cortisol levels alongside its dominant GH-releasing effect — establishing the multi-hormone profile that distinguishes GHRP-2 from selective analogs like ipamorelin.
Study 2 — GHRP-2 Pituitary Responsiveness in Critical Illness: Synergy with GHRH
Authors: Van den Berghe G, de Zegher F, Bowers CY, Wouters P, Muller P, Soetens F, Vlasselaers D, Schetz M, Verwaest C, Lauwers P, Bouillon R (University of Leuven, with Cyril Bowers) Year: 1996 Journal: Clinical Endocrinology PMID: 8949573 Full text: https://pubmed.ncbi.nlm.nih.gov/8949573/
This was the foundational study establishing GHRP-2’s clinical pharmacology in critically ill patients — a research area that would become a major series of publications from the Van den Berghe group at the University of Leuven documenting the neuroendocrine changes of prolonged critical illness and the potential of GH secretagogues to restore pituitary function.
40 critically ill adults received two IV boluses at 6-hour intervals of GHRH alone, GHRP-2 alone, GHRH+GHRP-2, TRH, or combinations in a crossover design.
Critically ill patients showed a striking GH response to GHRP-2 with mean peak GH of 51 micrograms/L in older patients and 102 micrograms/L in younger patients — significantly greater than placebo.
The mean GH response to GHRP-2 was more than fourfold higher than to GHRH alone (P equal to 0.007). The mean GH response to GHRH+GHRP-2 was 2.5-fold higher than to GHRP-2 alone (P equal to 0.01), confirming synergism between the two receptor pathways even in severely ill patients with suppressed endogenous GH secretion.
GHRP-2 increased basal serum cortisol levels by 35% (P equal to 0.02), confirming the HPA axis stimulation seen in healthy subjects.
The authors concluded that the striking GH bursts elicited by GHRP-2 and particularly by GHRH+GHRP-2 in patients with low spontaneous GH peaks opens therapeutic perspectives for GH secretagogues in critical care medicine — establishing the research rationale for subsequent multi-day infusion trials in prolonged critical illness.
Study 3 — Multi-Day GHRP-2 Infusion in Prolonged Critical Illness: GH, Thyroid, and Metabolic Effects
Authors: Van den Berghe G, de Zegher F, Baxter RC, Veldhuis JD, Wouters P et al. Year: 1998 Journal: Journal of Clinical Endocrinology and Metabolism PMID: 9467533 Full text: https://pubmed.ncbi.nlm.nih.gov/9467533/
This clinical trial in 20 critically ill adult patients (ill for several weeks) examined the effects of continuous intravenous infusions of TRH, GHRP-2, and GHRH+GHRP-2 over multiple nights, extending the single-bolus findings from the 1996 study into sustained infusion protocols.
GHRP-2 infusion amplified pulsatile GH secretion more than 6-fold, generating a 66% mean increase in serum IGF-1 within 45 hours. GHRH+GHRP-2 combined amplified pulsatile GH secretion more than 10-fold, generating a 106% mean increase in serum IGF-1 — confirming durable synergy over continuous infusion.
The combined TRH+GHRP-2 infusion increased pulsatile TSH secretion 4-fold and produced average rises in T4 of 40 to 54% and T3 of 52 to 116% without increasing reverse T3 — demonstrating that the GHRP-2 combination reactivated both the somatotropic and thyrotropic axes without driving thyroid hormone into the inactive rT3 form.
No effects on serum cortisol were detected during the multi-day continuous infusion period, suggesting that the acute cortisol stimulation from single bolus GHRP-2 doses attenuates with sustained infusion — an important observation for chronic protocol design.
The authors concluded that GHRP-2 combined with TRH represents a strategy to simultaneously reactivate two suppressed anterior pituitary axes in prolonged critical illness through the use of endogenous releasing hormone combinations.
Study 4 — GHRP-2 Increases Food Intake in Healthy Men: First Human Orexigenic Data
Authors: Laferrere B, Abraham C, Russell CD, Bowers CY (Columbia University with Cyril Bowers) Year: 2005 Journal: Journal of Clinical Endocrinology and Metabolism (PMC) PMID: 15699539 Full text: https://pmc.ncbi.nlm.nih.gov/articles/PMC2824650/
This controlled crossover study in 7 lean healthy males provided the first published demonstration that GHRP-2 increases food intake in humans, confirming its ghrelin-mimetic orexigenic properties through a controlled buffet meal paradigm.
Subjects subcutaneously infused with GHRP-2 at 1 microgram/kg/h for 270 minutes ate 35.9% more than when infused with saline (136.0 plus or minus 13.0 kJ/kg versus 101.3 plus or minus 10.5 kJ/kg, P equal to 0.008), with every single subject increasing food intake on GHRP-2 versus saline.
The macronutrient composition of consumed food was not different between conditions — subjects ate proportionally more of all macronutrients rather than selectively increasing intake of a specific nutrient class.
Serum GH levels rose significantly during GHRP-2 infusion (AUC 5,550 plus or minus 1,090 micrograms/L/240 min versus 412 plus or minus 161 for saline, P equal to 0.003), confirming expected GH secretagogue activity alongside the appetite stimulation.
The authors concluded that GHRP-2, like ghrelin, increases food intake in humans, suggesting it is a valuable tool for investigating ghrelin effects on eating behavior — establishing GHRP-2 as a pharmacological research probe for ghrelin receptor-mediated appetite and energy homeostasis research in human subjects.
Study 5 — GHRP-2 Synchronizes Pituitary Hormone Release in Critical Illness
Authors: Van den Berghe G, Wouters P, Bowers CY, de Zegher F, Bouillon R, Veldhuis JD Year: 1999 Journal: European Journal of Endocrinology PMID: 10037246 Full text: https://pubmed.ncbi.nlm.nih.gov/10037246/
This study examined whether GHRP-2, GHRH, and TRH would synchronize the secretory patterns of GH, TSH, and prolactin in critically ill patients — investigating whether the presumed endogenous GHRP-like ligand (later identified as ghrelin) participates in coordinated anterior pituitary hormone release.
During prolonged critical illness, nocturnal pulsatile secretion of GH, TSH, and prolactin is uniformly reduced but remains responsive to the continuous infusion of GH secretagogues and TRH.
GHRP-2 infusion, but not GHRH or TRH, produced synchronization of GH, TSH, and prolactin secretory patterns — suggesting that the endogenous ghrelin/GHRP-like ligand may participate in the orchestration of coordinated anterior pituitary hormone release under normal physiological conditions.
This finding contributed to the understanding that ghrelin (and its synthetic analogs like GHRP-2) may function not merely as a GH secretagogue but as a broader pituitary coordinating signal — a biological role beyond the classical two-hormone GHRH/somatostatin model of GH regulation.
The authors concluded that the synchronizing effect of an exogenous GHRP-2 drive, but not of GHRH or TRH, suggests that the presumed endogenous GHRP-like ligand participates in the orchestration of coordinated anterior pituitary hormone release.
GHRP-2 in the GHRP Class: Comparative Profile
GHRP-2 occupies a specific position within the broader family of GH secretagogues. The following comparative context helps clarify when GHRP-2 is the preferred research tool versus other class members.
Versus GHRP-6: GHRP-6 was the first characterized GHRP and shares the same GHS-R1a mechanism. GHRP-6 produces stronger appetite stimulation and cortisol elevation than GHRP-2 at equivalent GH-releasing doses. GHRP-2 is generally considered more potent in GH release per unit dose. GHRP-6 has been more extensively studied for cardioprotective and cytoprotective properties.
Versus ipamorelin: Ipamorelin was developed specifically to achieve GHS-R1a selectivity, producing GH release without the ACTH, cortisol, and prolactin elevations seen with GHRP-2. For experiments where clean GH axis stimulation without HPA confounders is required, ipamorelin is generally preferred. GHRP-2 is preferred when HPA axis interaction is itself a subject of investigation.
Versus hexarelin: Hexarelin is the most potent acute GH releaser among the GHRP class but produces the most pronounced cortisol, ACTH, and prolactin effects and shows the most rapid tachyphylaxis with repeated dosing. GHRP-2 produces similar GH potency to hexarelin in published direct comparisons with a generally more sustained response profile.
Versus GHRH: GHRP-2 consistently produces greater acute GH responses than maximal GHRH doses in published human data, but acts through a different receptor. The combination of GHRP-2 with GHRH or GHRH analogs produces synergistic responses reflecting simultaneous dual-receptor activation.
Cytoprotective and Cardioprotective Research Context
The GHRP family including GHRP-2 has been identified in published research as possessing broad cytoprotective and cardioprotective properties operating partially independently of GH release. Published research from multiple laboratories has demonstrated that GHRPs can protect cardiac cells from ischemia/reperfusion injury, reduce cardiomyocyte apoptosis, and improve cardiac function in experimental models — effects attributed to direct GHS-R1a receptor activation in cardiac tissue rather than to downstream GH/IGF-1 axis stimulation. This second research direction — cytoprotection rather than GH secretagogy — represents an active area of investigation for the entire GHRP class.
Critical Illness Research — A Significant Human Evidence Base
The Van den Berghe group series from the University of Leuven (1996 through 2002) represents the most rigorous published human clinical data for any GHRP compound, involving multiple randomized crossover clinical trials in ICU patients and establishing that GHRP-2 infusion can restore blunted pulsatile GH secretion in prolonged critical illness with a safer profile than exogenous recombinant GH (which was found to increase mortality in critically ill patients). This body of work established the physiological principle that pituitary secretagogue combinations — rather than supraphysiological exogenous hormone replacement — represent a more physiologically appropriate approach to neuroendocrine support in critical illness, and positioned GHRP-2 as a key tool for studying this approach.
An Important Regulatory and Safety Note
GHRP-2 (pralmorelin) is the only GHS-R1a peptide agonist with any regulatory approval anywhere in the world, holding Japanese approval for the specific diagnostic indication of growth hormone deficiency assessment. This regulatory history means GHRP-2 has an established pharmaceutical-grade safety dataset from both clinical trial programs and post-marketing diagnostic use in Japan that is not available for most other research peptides in this catalog.
The most well-characterized adverse effects at GH-releasing doses are cortisol and ACTH elevation (quantitatively similar to hCRH at standard diagnostic doses), mild prolactin elevation, and transient appetite stimulation. The potential for tachyphylaxis with chronic repeated dosing exists and has been observed in some protocols. Theoretical concerns with chronic high-dose use include insulin resistance from sustained GH axis activation.
Current Research Status
GHRP-2 is approved in Japan for diagnostic GH deficiency assessment (GHRP Kaken 100). It is not approved by the FDA for any indication. Research applications include GH axis pharmacology, ghrelin receptor biology, appetite and energy homeostasis research, critical illness neuroendocrinology, cytoprotection and cardioprotection investigation, and as a component of synergistic GH-stimulating combinations with GHRH analogs.
Reconstitution Note
GHRP-2 is a synthetic peptide. Bacteriostatic water is the standard reconstitution solvent. GHRP-2 dissolves readily in bacteriostatic water without requiring acidic solvents. Always confirm the recommended solvent against the specific lot datasheet before reconstitution.
In-Use Period and Storage
Before Reconstitution — Lyophilized Powder
Rogue Compounds stores all products refrigerated prior to shipping to maintain compound integrity from production through to delivery. Upon receipt researchers should store vials at 2 to 8 degrees Celsius immediately. Keep vials sealed, dry, and away from direct light until ready for use. Do not freeze. Repeated freeze-thaw cycling has been documented in peer-reviewed pharmaceutical formulation literature to accelerate structural degradation even in dry powder form, potentially compromising molecular integrity and experimental reproducibility.
Why We Refrigerate Instead of Freeze
Freezing and thawing introduces mechanical and osmotic stress at the molecular level. Published pharmaceutical research identifies freeze-thaw cycling as a significant risk factor for loss of structural integrity in peptides and protein-based compounds. To protect compound quality at every stage of handling and fulfillment, Rogue Compounds maintains refrigerated rather than frozen cold chain storage throughout the entire process.
After Reconstitution — Liquid Solution
Store reconstituted solutions refrigerated at 2 to 8 degrees Celsius immediately after preparation. Protect from light at all stages of storage and handling. Avoid repeated freeze-thaw cycles of reconstituted solutions regardless of the diluent used. Use within the timeframe recommended for the individual compound. Label each aliquot with the compound name, concentration, date of reconstitution, and diluent used. Discard any solution that shows visible particulate matter, discoloration, or signs of contamination.
Note: Storage and in-use recommendations on this page are provided as general laboratory guidance based on standard peptide handling practices documented in peer-reviewed pharmaceutical literature. Researchers should always refer to the individual compound’s published research literature and datasheet for any specific requirements. All products sold by Rogue Compounds are intended strictly for in-vitro laboratory research use only.
Available from Rogue Compounds
View the GHRP-2 product page: https://roguecompounds.com/product/ghrp-2/