GHRP-2

GHRP-2, also known by its International Nonproprietary Name (INN) pralmorelin, is a synthetic hexapeptide growth hormone secretagogue composed of six amino acids in the sequence D-Ala-D-βNal-Ala-Trp-D-Phe-Lys-NH2 ⁽¹⁾. It was developed during the 1990s by researchers at Tulane University and Polygen (Germany) as a second-generation improvement on the original GHRP-6 compound, to achieve stronger growth hormone output and a cleaner side-effect profile ⁽²⁾. GHRP-2 is classified as a ghrelin mimetic, meaning it replicates the signaling (also spelled signaling) activity of ghrelin, the endogenous 28-amino-acid “hunger hormone” produced primarily in the gastrointestinal tract ⁽³⁾.

What sets GHRP-2 apart from other secretagogues is its potency. On a microgram-for-microgram basis, it produces a larger GH response than GHRP-6, Ipamorelin, or native GHRH itself ^(2,4). Clinical data in healthy young adults showed that intravenous GHRP-2 at 1 μg/kg elicited a GH response significantly greater (p < 0.05) than the maximal effective dose of GHRH ⁽⁴⁾. This potency, combined with its oral bioavailability and multiple viable routes of administration (subcutaneous, intranasal, intravenous, oral), has made GHRP-2 one of the most studied peptides in the growth hormone secretagogue class ^(1,2).

GHRP-2 holds a unique regulatory distinction: it is the only growth hormone-releasing peptide approved for clinical use worldwide. Kaken Pharmaceutical markets it in Japan under the brand name GHRP Kaken 100 as a single-dose diagnostic agent for assessing pituitary GH reserve in patients suspected of growth hormone deficiency ^(1,5). It is not FDA-approved in the United States and has not been placed on the FDA’s Category 2 list of substances nominated for bulk compounding evaluation. All Healius Peptides GHRP-2 is sold strictly for in vitro research purposes.

GHRP-2 drives growth hormone secretion through a mechanism entirely separate from the GHRH receptor pathway. Its primary target is the growth hormone secretagogue receptor type 1a (GHS-R1a), a G-protein-coupled receptor expressed on somatotroph cells in the anterior pituitary gland as well as in hypothalamic nuclei and peripheral tissues, including the liver, pancreas, and GI tract ^(1,3).

When GHRP-2 binds GHS-R1a, it activates phospholipase C (PLC), which generates inositol triphosphate (IP3) and diacylglycerol (DAG). IP3 triggers intracellular calcium release from the endoplasmic reticulum, raising cytosolic calcium levels in somatotrophs and prompting exocytosis of stored GH vesicles ^(3,6). In parallel, DAG activates protein kinase C (PKC), which amplifies the secretory signal. A secondary signaling arm involves cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA), further reinforcing GH output ⁽⁶⁾.

GHRP-2 also acts at the hypothalamic level. Data from animal models indicate that it stimulates hypothalamic neurons to increase endogenous GHRH release while simultaneously suppressing somatostatin (growth hormone-inhibiting hormone), effectively removing the brake on pituitary GH secretion ^(3,6). This dual action, amplifying the positive signal while dampening the negative one, is a key reason GHRP-2 produces such pronounced GH elevations compared to agents that target only one of these pathways.

Because the GHS-R1a pathway and the GHRH receptor pathway converge on the same somatotroph cells through different intracellular cascades, GHRP-2 and GHRH-class compounds such as CJC-1295 (Mod GRF 1-29) or Sermorelin produce a well-characterized (also spelled characterized) synergistic effect when co-administered. Studies have reported a 2- to 3-fold greater GH release from the combination than from either compound alone ^(2,7).

Growth Hormone Secretion

The primary research application of GHRP-2 is its ability to stimulate robust, pulsatile GH release. Clinical pharmacokinetic data show peak plasma GH concentrations of 30 to 100 ng/mL within 15 to 30 minutes of subcutaneous administration, representing an 8- to 20-fold increase over baseline, depending on dose and individual variability ⁽²⁾. Importantly, GHRP-2 remains effective in older subjects: while age-related decline in GH responsiveness occurs, the peptide still produces GH elevations significantly above those achievable with GHRH alone in elderly populations (aged 66 to 73) ⁽⁴⁾.

Muscle Protein Metabolism

Animal model data in yaks demonstrated that GHRP-2 administration increased muscle protein deposition through two parallel mechanisms: elevated protein synthesis driven by GH and IGF-1 upregulation, and reduced protein degradation via dose-dependent suppression of the muscle atrophy markers atrogin-1 and MuRF1 ⁽⁸⁾. The researchers noted that GHRP-2 attenuated dexamethasone-induced expression of both ubiquitin ligases in a dose-dependent manner, suggesting a protective role against catabolic muscle wasting in research models.

Appetite and Metabolic Regulation

As a ghrelin receptor agonist, GHRP-2 activates orexigenic pathways in the hypothalamic arcuate nucleus. A controlled human study found that GHRP-2 administration increased food intake by approximately 36% over a 4.5-hour observation window compared to saline controls ⁽⁹⁾. This appetite-stimulating effect, while moderate relative to GHRP-6, positions GHRP-2 as a research tool for investigating ghrelin-mediated feeding behavior (also spelled behavior) and cachexia models.

Sleep Architecture

Polysomnography studies in healthy volunteers showed that evening administration of GHRP-2 increased the duration of slow-wave sleep (stages 3 and 4) by roughly 25% and increased the amplitude of nocturnal GH pulses by 40 to 60% compared to placebo ⁽¹⁰⁾. The correlation between deeper sleep and greater GH output has implications for aging (also spelled aging) research and recovery-focused study designs.

Cardioprotective Activity

In vitro studies using damaged cardiac cell lines suggest GHRP-2 may reduce cardiomyocyte apoptosis following ischemic insult ⁽¹¹⁾. Research into GHRP-2 analog Hexarelin has identified cardiac-specific receptors distinct from GHS-R1a, raising the question of whether some cardioprotective effects of GHRP-class peptides operate independently of growth hormone release ⁽¹¹⁾.

Healius Peptides supplies GHRP-2 as a 5mg lyophilized powder in a sealed, sterile vial. Reconstitution requires bacteriostatic water (BAC water), which contains 0.9% benzyl alcohol as a preservative and allows multiple withdrawals from the same vial over its storage life.

Reconstitution

Using a sterile syringe, draw the desired volume of BAC water and inject it slowly down the inside wall of the vial. Do not aim the stream directly at the lyophilized pellet, as this can denature the peptide. Allow the powder to dissolve naturally; gently swirl the vial if needed, but do not shake it. The solution should be clear and free of particulate matter before use. Use our GHRP-2 dosage calculator to determine the correct reconstitution volume for your target concentration.

Research Dosage Ranges

In published clinical and preclinical protocols, GHRP-2 doses typically range from 1 to 2 μg/kg body weight per administration, administered intravenously or subcutaneously ^(4,5). Dose-response data show optimal GH stimulation in the 100 to 300 μg range, with diminishing returns at higher doses due to receptor saturation effects ⁽²⁾. Higher doses (above 200 μg) are associated with a greater likelihood of secondary hormonal effects, including elevations in cortisol and prolactin ^(4,12).

Storage

Store unreconstituted GHRP-2 at -20°C for long-term stability. Once reconstituted with BAC water, store the vial at 2 to 8°C (standard refrigerator temperature) and use within 14 to 21 days. Avoid repeated freeze-thaw cycles. Protect from direct light.

GHRP-2 is generally well tolerated at standard research doses. A 5-day repeated-dose study administering 100 μg GHRP-2 subcutaneously to healthy human subjects reported no adverse events or toxicities, with cortisol and prolactin levels remaining within normal ranges throughout ^(5,12). That said, the peptide’s hormonal profile is not entirely GH-selective, and researchers should be aware of the following dose-dependent effects observed across published trials.

Cortisol and ACTH Elevation

The 1997 University of Turin study comparing GHRP-2 and Hexarelin found that both peptides stimulated ACTH and cortisol secretion at levels comparable to human corticotropin-releasing hormone (hCRH) ⁽⁴⁾. These elevations are transient, typically returning to baseline within 2 to 3 hours, but become more pronounced at doses above 200 μg ^(4,12). Compared to GHRP-6, the cortisol response to GHRP-2 is broadly similar at equivalent doses.

Prolactin Elevation

GHRP-2 produces a mild, dose-dependent increase in prolactin. In clinical comparisons, the prolactin-releasing effect of GHRP-2 was significantly lower (p < 0.01) than that of thyrotropin-releasing hormone (TRH), and the response showed attenuation over repeated daily dosing ^(4,12). At standard research doses, prolactin elevations are modest and self-limiting.

Appetite Stimulation

Through its agonism of the ghrelin receptor, GHRP-2 increases hunger. The effect is real but moderate, notably less intense than GHRP-6, which acts on additional appetite-related pathways ^(2,9). Researchers working with animal models should account for this orexigenic effect when designing feeding protocols.

Other Reported Effects

At higher or prolonged doses in clinical settings, reported effects include transient water retention, mild injection-site flushing, and temporary decreases in insulin sensitivity ⁽¹²⁾. No serious adverse events have been documented in published GHRP-2 clinical trial literature.

GHRP-2 and GHRP-6 are synthetic hexapeptide growth hormone secretagogues that act on the ghrelin receptor (GHS-R1a) and were both developed from the same foundational research at Tulane University. They share the same core mechanism and produce overlapping downstream effects. The differences between them come down to potency, selectivity, and side-effect burden.

GH Release Potency

GHRP-2 is the more potent GH secretagogue. Head-to-head clinical data in healthy young adults showed that GHRP-2 and Hexarelin (a GHRP-2 analog) produced stronger GH responses than GHRP-6 at matched doses, with GHRP-2 consistently outperforming GHRH itself ⁽⁴⁾. Peak plasma GH after subcutaneous GHRP-2 reaches 30 to 100 ng/mL, and on a dose-adjusted basis, GHRP-2 achieves higher peak concentrations and area-under-the-curve values than GHRP-6 ⁽²⁾.

Appetite Stimulation

This is the most practical difference between the two. GHRP-6 triggers a strong, sometimes overwhelming hunger response that can complicate research protocols that measure food intake or involve caloric restriction. GHRP-2 also stimulates appetite, but the effect is substantially milder ^(2,9). For research designs where appetite is a confounding variable, GHRP-2 is the preferred choice.

Cortisol and Prolactin

Both peptides elevate ACTH, cortisol, and prolactin to a similar extent at equivalent doses ⁽⁴⁾. Neither peptide is “clean” in the way that Ipamorelin is (Ipamorelin produces virtually no cortisol or prolactin elevation at GH-stimulating doses). Researchers who need maximum GH output and can tolerate moderate secondary hormonal effects will favor (also spelled favor) GHRP-2 for its superior potency; those who need hormonal selectivity should consider Ipamorelin.

Summary

Choose GHRP-2 when the research protocol demands the highest possible GH output from the GHRP class, and appetite stimulation is either acceptable or a desired endpoint. Choose GHRP-6 when strong appetite stimulation is itself the research variable, or when budget is the primary constraint (GHRP-6 is typically the lower-cost option). For protocols requiring minimal off-target hormonal effects, Ipamorelin remains the most selective alternative.

1. Pralmorelin (GHRP-2). Wikipedia / PubChem Compound Summary. Growth hormone-releasing peptide 2 (pralmorelin), a synthetic hexapeptide GHS-R1a agonist, amino acid sequence D-Ala-D-βNal-Ala-Trp-D-Phe-Lys-NH2, molecular weight 817.9 Da. First GHS to enter clinical use; approved in Japan (Kaken Pharmaceutical, GHRP Kaken 100) as a diagnostic agent for GH deficiency.

2. Growth Hormone Secretagogues: Mechanism of Action and Clinical Development. JCSM Rapid Communications, 2020. Review of GHRP-2 potency profile, clinical pharmacokinetics (peak GH 30-100 ng/mL, 8-20-fold above baseline), comparison with GHRP-6 and Ipamorelin, synergistic effects with GHRH analogs (2-3-fold amplification), and dose-response characteristics.

3. Growth Hormone Secretagogue Receptor (GHS-R1a). Receptor pharmacology reference. GHS-R1a is a G-protein-coupled receptor expressed in the pituitary, hypothalamus, and peripheral tissues—Ghrelin as an endogenous ligand. GHRP-2 binding activates PLC/IP3/PKC and cAMP/PKA signaling cascades. Hypothalamic effects on GHRH release and somatostatin suppression.

4. Arvat E, Di Vito L, Maccagno B, et al. Effects of GHRP-2 and Hexarelin, two synthetic GH-releasing peptides, on GH, prolactin, ACTH, and cortisol levels in man. Peptides. 1997;18(6):885-891. Key findings: GHRP-2 and Hexarelin produce similar, dose-dependent GH responses exceeding GHRH (p < 0.05). PRL response lower than TRH (p < 0.01). ACTH/cortisol response comparable to hCRH. Age-dependent decline in older people (66-73 yr), but still exceeding GHRH.

5. Furuta S, Shimada O, Doi N, et al. General pharmacology of KP-102 (GHRP-2), a potent growth hormone-releasing peptide. Arzneimittelforschung. 2004;54(12):868-880. Safety and pharmacological profile of GHRP-2 (KP-102). Diagnostic utility for GH deficiency. GH peak cut-off value of 15.0 μg/L for identifying GHD. Clinical use in Japan by Kaken Pharmaceutical.

6. Roh SG, He ML, Matsunaga N, et al. Mechanisms of action of growth hormone-releasing peptide-2 in bovine pituitary cells. Journal of Animal Science. 1997;75(10):2744-2748. GHRP-2 mechanism in pituitary cells via GHS receptor interactions, calcium channel activation, cAMP pathway, and protein kinase C activation, contributing to GH elevation.

7. Spalding M, Barber L, et al. Retrospective review of GHRP/Sermorelin therapy on IGF-1 levels in men on testosterone therapy. Sexual Medicine Reviews, 2018. 14 men, 100 μg GHRP-6/GHRP-2 + Sermorelin three times daily. Mean IGF-1 increased from 159.5 to 239.0 ng/mL (p < 0.0001). Mean treatment duration is 134 days.

8. Hu R, Wang Z, Peng Q, et al. Effects of GHRP-2 and Cysteamine Administration on Growth Performance, Somatotropic Axis Hormone, and Muscle Protein Deposition in Yaks. Journal of Animal Science. 2016. GHRP-2 increased muscle protein deposition and attenuated dexamethasone-induced atrogin-1 and MuRF1 expression dose-dependently.

9. Laferrere B, Abraham C, Russell CD, Bowers CY. Growth hormone-releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men. Journal of Clinical Endocrinology and Metabolism. 2005;90(2):611-614. The GHRP-2 group showed a ~36% increase in food consumption over 4.5 hours compared with saline controls.

10. Copinschi G, et al. Effects of GHRP-2 on sleep architecture and nocturnal GH release. Polysomnography study in healthy volunteers. Evening GHRP-2 enhanced slow-wave sleep duration by ~25% and nocturnal GH pulse amplitude by 40-60% versus placebo.

11. GHRP-2 cardioprotective research. In vitro studies in damaged cardiac cell culture lines show reduced cardiomyocyte apoptosis following ischemic insult. Related research on Hexarelin has identified cardiac-specific receptors distinct from GHS-R1a.

12. Camanni F, Ghigo E, Arvat E. Growth hormone-releasing peptides and their analogs. Frontiers in Neuroendocrinology. 1998;19(1):47-72. Review of GHRP-2 dose-dependent effects on prolactin, ACTH, and cortisol—attenuation of PRL response over repeated dosing. Optimal dose range 100-300 μg for GH stimulation with manageable secondary hormonal effects.

13. Raun K, Hansen BS, Johansen NL, et al. Ipamorelin is the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998;139(5):552-561. Ipamorelin is the most GH-selective secretagogue: no effect on ACTH, cortisol, or prolactin at GH-stimulating doses. Comparison benchmark for GHRP-2 selectivity profile.

This product is intended for laboratory research use only. It is not a drug, food, cosmetic, or dietary supplement, and it is not intended for human or veterinary consumption. The U.S. Food and Drug Administration has not approved GHRP-2 (pralmorelin) for any therapeutic indication. All information provided in this document is drawn from published, peer-reviewed scientific literature and is intended solely to support researchers in designing and interpreting in vitro studies. Healius Peptides makes no claims regarding the safety, efficacy, or suitability of this product for any use other than laboratory research. Buyers accept full responsibility for ensuring their use complies with all applicable local, state, federal, and international regulations.