GHRP-2 (growth hormone releasing peptide-2), also known by its pharmaceutical name pralmorelin, is a synthetic hexapeptide composed of six amino acids (D-Ala-D-2Nal-Ala-Trp-D-Phe-Lys-NH2) that stimulates the pituitary gland to release growth hormone. With a molecular weight of 817.97 g/mol and the CAS number 158861-67-7, it is widely regarded as the most potent member of the traditional GHRP family by peak GH output.
Developed through the pioneering work of endocrinologist Cyril Y. Bowers in the 1980s and 1990s, GHRP-2 occupies a middle ground among growth hormone secretagogues: it delivers stronger GH release than GHRP-6 or ipamorelin while producing a comparatively cleaner hormonal profile than GHRP-6, with less appetite stimulation and moderate rather than pronounced effects on cortisol and prolactin. Approved in Japan as a diagnostic agent for growth hormone deficiency, it remains unapproved by the FDA in the United States and is prohibited by WADA in all sports.
Primary effects include:
- Potent stimulation of pulsatile growth hormone release
- Elevation of IGF-1 levels via the GH/IGF-1 axis
- Moderate appetite stimulation (less than GHRP-6)
- Improved recovery from exercise and injury
- Enhanced sleep quality, particularly slow-wave sleep
- Potential improvements in body composition and skin quality
What Is GHRP-2?
GHRP-2 is a synthetic hexapeptide belonging to the growth hormone secretagogue (GHS) class of compounds. Its sequence, D-Ala-D-2Nal-Ala-Trp-D-Phe-Lys-NH2, incorporates unnatural D-amino acids that confer resistance to enzymatic degradation and improve receptor binding affinity compared to earlier peptides in the series.
The GHRP lineage began in 1984 when Bowers demonstrated that chemical analogs of met-enkephalin exhibited unexpected GH-releasing activity in pituitary cell cultures. GHRP-6 emerged as the first clinically studied member of the family, followed by GHRP-1, GHRP-2, and hexarelin. Among these, GHRP-2 was optimized for higher GH-releasing potency and a more favorable secondary hormone profile.
In Japan, GHRP-2 is marketed under the name pralmorelin (brand name GHRP Kaken) by Kaken Pharmaceutical. It received regulatory approval from the Pharmaceuticals and Medical Devices Agency (PMDA) in October 2004 as a diagnostic tool for assessing GH deficiency in adults and children over four years of age. Kaken sublicensed North American rights to Wyeth, but the compound never advanced to FDA approval.
GHRP-2 is distinct from the other major GHRPs in meaningful ways. Compared to GHRP-6, it produces higher peak GH levels with less pronounced hunger, cortisol elevation, and prolactin stimulation. Compared to ipamorelin, which is considered the most selective GHRP, GHRP-2 achieves greater absolute GH output but at the cost of moderate effects on the ACTH-cortisol axis and prolactin secretion that ipamorelin avoids entirely.
How It Works
GHS-R1a Receptor Agonism
GHRP-2 functions as an agonist of the growth hormone secretagogue receptor type 1a (GHS-R1a), the same receptor that responds to the endogenous hormone ghrelin. GHS-R1a is a G-protein coupled receptor expressed primarily on somatotroph cells in the anterior pituitary gland and in the hypothalamic arcuate nucleus.
Upon binding, GHRP-2 activates Gq/11 signaling pathways, leading to phospholipase C activation and the generation of inositol trisphosphate (IP3) and diacylglycerol (DAG). This cascade mobilizes calcium from intracellular stores, triggering exocytosis of GH-containing secretory granules and producing acute GH release. Beyond GHS-R1a, GHRPs also interact with the CD36 scavenger receptor, which appears to mediate some of their documented cytoprotective and cardiovascular effects.
Unlike exogenous GH administration, GHRP-2 works within the body's endogenous feedback loops. Somatostatin-mediated negative feedback remains intact, which means GHRP-2 amplifies natural GH pulses rather than creating a constant supraphysiological elevation. This built-in regulatory mechanism makes it difficult to overshoot GH levels to a dangerous degree.
Growth Hormone Release Profile
GHRP-2 is among the most potent GH secretagogues by peak output. Clinical data show that a single subcutaneous injection produces peak plasma GH concentrations of 30 to 100 ng/mL within 15 to 30 minutes, representing 8- to 20-fold increases above baseline depending on dose and individual response.
In the pivotal comparative study by Arvat et al. (1997), GHRP-2 at 1 mcg/kg produced GH responses that exceeded those induced by the maximal effective dose of GHRH in healthy young adults, based on intravenous administration in a controlled clinical setting. The GH-releasing effect is dose-dependent up to approximately 2 mcg/kg, beyond which a plateau occurs. Co-administration with GHRH analogs produces synergistic effects, with combined GH responses two to three times greater than either agent alone.
In the Japanese diagnostic application, plasma GH levels after a single pralmorelin injection exceed 15 mcg/L in healthy subjects but remain below 15 mcg/L in patients with severe GH deficiency, forming the basis of its use as a provocative test.
Effects on Cortisol and Prolactin
GHRP-2 produces moderate stimulation of the ACTH-cortisol axis and prolactin secretion. Arvat et al. demonstrated that all tested doses of GHRP-2 stimulated ACTH and cortisol to a similar extent, with responses comparable to those produced by human corticotropin-releasing hormone (hCRH). Prolactin elevation was present but lower than that induced by thyrotropin-releasing hormone (TRH).
This profile positions GHRP-2 between GHRP-6 (which tends to produce stronger cortisol and prolactin spikes) and ipamorelin (which does not meaningfully affect either hormone even at doses exceeding 200 times its GH-releasing ED50). For users concerned about cortisol-related effects such as impaired recovery or sleep disruption, or prolactin-related effects such as reduced libido, the moderate profile of GHRP-2 is a relevant consideration when choosing among GHRPs.
Appetite Stimulation
As a ghrelin receptor agonist, GHRP-2 stimulates appetite. A controlled study by Laferrere et al. (2005) published in the Journal of Clinical Endocrinology & Metabolism confirmed that GHRP-2 increases food intake in healthy men through ghrelin-mediated pathways.
However, the appetite effect is moderate compared to GHRP-6, which triggers robust, acute hunger shortly after dosing. This distinction matters in practice: users pursuing body recomposition or fat loss often prefer GHRP-2 or ipamorelin over GHRP-6 specifically because the hunger response is more manageable and less likely to derail dietary adherence.
Dosage Protocols
No FDA-approved dosing guidelines exist for GHRP-2. The following protocols are derived from clinical research and practitioner experience:
- Standard range: 100 to 300 mcg per injection, administered subcutaneously one to three times daily
- Saturation dose: Approximately 1 to 2 mcg/kg body weight per injection, beyond which additional GH release plateaus
- Most common protocol: 100 to 200 mcg at bedtime, as this amplifies the natural nocturnal GH surge
Beginner Protocol
100 mcg once daily before bed, for 8 to 12 weeks. The bedtime dose is the single most important administration window because it coincides with the body's largest endogenous GH pulse.
Intermediate Protocol
150 to 200 mcg, two times daily (morning fasted and before bed), for 8 to 12 weeks. Adding a morning dose captures a second GH pulse opportunity while fasting insulin levels are low.
Advanced Protocol
200 to 300 mcg, two to three times daily, often combined with a GHRH analog such as CJC-1295 (no DAC) or Mod GRF 1-29, for 8 to 16 weeks. The synergy between GHRP-2 and a GHRH analog can amplify GH output two to three times beyond either peptide alone.
Cycling Recommendations
Cycling is recommended to maintain receptor sensitivity. A common approach is 8 to 12 weeks on followed by 4 to 8 weeks off. The peptide cycling guide covers protocols in more detail. Some practitioners use a 5-days-on, 2-days-off weekly schedule to reduce the risk of tachyphylaxis. A clinical study by Bowers et al. noted response attenuation after five consecutive days of GHRP-2 injections, reinforcing the rationale for periodic breaks.
Timing Considerations
GHRP-2 should be administered on an empty stomach, at least 30 minutes before eating or two or more hours after a meal. Elevated blood glucose and insulin significantly blunt the GH response. For the same reason, high-glycemic meals should be avoided around dosing windows.
How to Use / Administration Methods
GHRP-2 is administered via subcutaneous injection, typically into the abdominal fat, thigh, or deltoid region.
Injection process:
- Reconstitute the lyophilized powder with bacteriostatic water (see Reconstitution section below)
- Draw the calculated dose into an insulin syringe (29 to 31 gauge)
- Pinch a fold of skin at the injection site
- Insert the needle at a 45 to 90 degree angle
- Depress the plunger slowly and steadily
- Withdraw and dispose of the needle in a sharps container
Injection sites should be rotated to prevent lipodystrophy. Most users find subcutaneous abdominal injections the most convenient option. Intranasal formulations were investigated in clinical trials (KP-102 LN) but showed lower and less reliable bioavailability than injectable routes.
Results Timelines
Weeks 1 to 2:
- Improved sleep quality, often noticeable within the first few days (GHRP-2 is among the peptides covered in the best peptides for sleep guide)
- Vivid dreams correlating with enhanced slow-wave sleep architecture
- Mild increases in energy and subjective well-being
Weeks 3 to 4:
- Faster recovery from exercise becomes apparent
- Reduced muscle soreness and quicker return to baseline after intense training
- Some users report improved skin hydration
Weeks 6 to 8:
- Body composition changes become measurable, with gradual reductions in subcutaneous fat and improved muscle fullness
- Joint comfort and connective tissue resilience may improve
- Sleep quality benefits continue to consolidate
Weeks 10 to 12:
- More significant body composition shifts are typically observed
- Strength gains, enhanced recovery capacity, and improved overall vitality commonly reported
- Hair and nail growth improvements sometimes noted
Weeks 12 to 16+:
- Cumulative benefits reach their peak for users on extended cycles
- Most substantial improvements in body composition and anti-aging markers
- Consideration should be given to cycling off to preserve receptor sensitivity
Individual responses vary based on age, baseline GH production, diet, exercise habits, sleep quality, and genetic factors. Older individuals with lower baseline GH levels often report more pronounced effects.
Research Evidence
GH Stimulation and Diagnostic Use
The Japanese approval of pralmorelin was based on clinical data showing that a single intravenous dose reliably distinguishes GH-sufficient from GH-deficient subjects. Healthy individuals produce plasma GH responses above 15 mcg/L, while patients with severe adult GH deficiency consistently fall below this threshold. This led to pralmorelin's approval as a diagnostic provocative test in 2004.
Pediatric Growth Study
Mericq, Bowers, and colleagues (1998) conducted an eight-month study treating six prepubertal GH-deficient children with stepwise increasing subcutaneous doses of GHRP-2 (0.3, 1.0, and 3.0 mcg/kg/day). The study demonstrated dose-dependent increases in overnight episodic GH secretion, higher growth velocity during treatment compared to pre- and post-treatment periods, and no observed side effects or toxicities. A final two-month period combining GHRP-2 with GHRH produced further augmentation of GH output.
Comparative Hormonal Profiling
Arvat et al. (1997) conducted the definitive head-to-head comparison of GHRP-2, hexarelin, GHRH, TRH, and hCRH in healthy young adults. The study established that GHRP-2 and hexarelin produced GH responses exceeding maximal-dose GHRH, with similar slight stimulatory effects on prolactin (lower than TRH) and ACTH/cortisol (comparable to hCRH). This work remains a cornerstone reference for understanding GHRP-2's hormonal selectivity profile.
Appetite and Food Intake
Laferrere et al. (2005) demonstrated in a controlled crossover study that GHRP-2 significantly increases caloric intake in healthy men through ghrelin receptor-mediated appetite stimulation. This confirmed that GHRP-2, like endogenous ghrelin, has orexigenic properties, though clinical observation consistently shows the effect is less intense than that of GHRP-6.
Cytoprotective Properties
A comprehensive 2017 review by Berlanga-Acosta et al. catalogued evidence for GHRP-mediated cytoprotection, documenting cardioprotective, neuroprotective, and anti-inflammatory effects in preclinical models. These effects appear to be mediated in part through CD36 receptor binding and are independent of GH release, suggesting additional therapeutic dimensions beyond growth hormone secretion.
Stacking
GHRP-2 + CJC-1295 (no DAC) / Mod GRF 1-29
This is the most widely used combination. The GHRH analog primes the pituitary somatotrophs while GHRP-2 amplifies the release signal through a separate receptor pathway, producing synergistic GH output that exceeds either agent alone by two to three times. See the peptide stacking guide for practical protocols combining these compounds. Typical dosing is 100 to 200 mcg of each peptide administered simultaneously in the same syringe, one to three times daily.
GHRP-2 + CJC-1295 (with DAC)
CJC-1295 with DAC has an extended half-life of approximately six to eight days, providing sustained baseline GHRH stimulation. Adding GHRP-2 injections on top of this creates acute GH pulses superimposed on a chronically elevated GHRH signal. This approach requires less frequent CJC-1295 dosing (once or twice weekly) but maintains daily GHRP-2 injections.
GHRP-2 + GHRH for Diagnostic Synergy
In clinical research settings, the combination of GHRP-2 with GHRH has been used as an enhanced provocative test for GH deficiency, leveraging the synergistic release to improve diagnostic sensitivity. The Mericq et al. (1998) pediatric study included a combined GHRP-2 + GHRH treatment arm that produced the highest GH responses observed.
When stacking, standard GHRP-2 dosing is maintained while the complementary peptide is added at its own standard dose. Timing rules (empty stomach, pre-bed priority) apply to both peptides.
Reconstitution, Storage & Prep
GHRP-2 is supplied as a lyophilized (freeze-dried) white powder requiring reconstitution before use.
Reconstitution Process:
- Allow the peptide vial to reach room temperature
- Using a sterile syringe, draw the desired volume of bacteriostatic water (typically 2.5 mL per 5 mg vial or 5 mL per 10 mg vial for convenient 1:1 dosing math)
- Inject the water slowly against the vial wall, letting it run down gently to avoid damaging the peptide
- Swirl gently until fully dissolved; never shake
- The solution should be clear and colorless
Dosing Calculation Example:
If reconstituting 5 mg with 2.5 mL bacteriostatic water, the concentration equals 2 mg/mL (2000 mcg/mL). For a 200 mcg dose, draw 0.1 mL (10 units on a standard U-100 insulin syringe).
Storage Guidelines:
- Unreconstituted powder: Store frozen at -20 degrees C for long-term stability, or refrigerated at 2 to 8 degrees C for shorter periods; stable for 12 or more months when frozen
- Reconstituted solution: Refrigerate at 2 to 8 degrees C (36 to 46 degrees F); use within 3 to 4 weeks for optimal potency
- Never freeze reconstituted peptides, as freeze-thaw cycles degrade the molecular structure
- Protect from light; keep vials in their original box or wrapped in foil
- Use bacteriostatic water (not sterile water) for multi-dose vials to prevent bacterial contamination
Side Effects
GHRP-2 is generally well-tolerated in clinical studies, with the intact somatostatin feedback loop providing a natural safety mechanism against GH overproduction.
Common (typically mild and transient):
- Increased appetite (moderate, less than GHRP-6)
- Flushing and warmth at the injection site or face
- Transient drowsiness or sleepiness, particularly with evening doses
- Mild water retention and peripheral edema
- Increased gastrointestinal motility
Less Common:
- Elevations in cortisol and ACTH (moderate, comparable to hCRH)
- Mild prolactin elevation (less than TRH-induced levels)
- Numbness or tingling in extremities
- Joint stiffness
- Lightheadedness post-injection
Rare or Theoretical Concerns:
- Impaired glucose metabolism and elevated blood glucose with prolonged use
- Potential tachyphylaxis (reduced response) with continuous daily dosing
- Theoretical promotion of existing malignancies through elevated GH/IGF-1 (applies to all GH-elevating compounds)
Side effect incidence tends to be lower than with exogenous hGH because GHRP-2 stimulates endogenous GH synthesis within physiological regulatory limits. The eight-month pediatric study by Mericq et al. reported no side effects or toxicities at any dose level tested.
Legal Status / FDA
GHRP-2 is not FDA-approved for any indication in the United States. Despite Kaken Pharmaceutical sublicensing North American rights to Wyeth, the compound never completed the FDA approval process. It reached Phase II clinical trials for GH deficiency and short stature in children but was not advanced to market.
In the United States, GHRP-2 exists in a regulatory gray area. It can be obtained as a research chemical, but it is not approved for human therapeutic use. The FDA has issued warning letters to pharmacies marketing GHRP-2 for human administration, and it is not available as a compounded medication through legitimate channels.
In Japan, pralmorelin (GHRP-2) is an approved pharmaceutical. It received PMDA approval in October 2004 and is marketed by Kaken Pharmaceutical as a single-dose diagnostic agent for assessing GH deficiency in adults and children over four years of age.
In Australia, peptides in this class are generally classified as Schedule 4 (prescription-only) substances. Regulations vary internationally and are subject to change; users should verify the legal status in their specific jurisdiction.
Sports / WADA
The World Anti-Doping Agency (WADA) explicitly prohibits GHRP-2 under Section S2.2.4 of the Prohibited List, which covers growth hormone releasing factors (GHRFs). This includes GH-releasing peptides such as GHRP-1, GHRP-2, GHRP-3, GHRP-4, GHRP-5, GHRP-6, and hexarelin, as well as growth hormone secretagogue mimetics like ipamorelin, ibutamoren, and macimorelin.
The prohibition applies at all times, both in-competition and out-of-competition. WADA-accredited laboratories can detect pralmorelin and its metabolites in urine samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS), as validated by Thomas et al. (2010).
Athletes subject to anti-doping testing in any capacity, including Olympic, professional, collegiate, and many amateur organizations, face suspension, loss of results, and career consequences if GHRP-2 or its metabolites are detected. There is no therapeutic use exemption pathway that would permit GHRP-2 use in active competition.
Conclusion
GHRP-2 occupies a distinct position in the growth hormone secretagogue landscape. It delivers the highest peak GH output among the traditional GHRPs while maintaining a meaningfully cleaner secondary hormone profile than GHRP-6, with moderate rather than pronounced effects on appetite, cortisol, and prolactin. Its approval in Japan as a diagnostic agent for GH deficiency provides a level of clinical validation that many research peptides lack entirely.
The compound's limitations are equally clear. It is less selective than ipamorelin, it does elevate cortisol and prolactin to a degree that some users find undesirable, and it remains unapproved by the FDA with limited long-term human safety data outside the diagnostic context. Its prohibition by WADA renders it incompatible with competitive athletics.
For individuals exploring GH secretagogues under appropriate medical guidance, GHRP-2 offers a potent middle-ground option: stronger than ipamorelin in raw GH output, cleaner than GHRP-6 in its hormonal side effects, and well-suited to synergistic stacking with GHRH analogs like CJC-1295. As with any unapproved compound, informed decision-making requires weighing the available evidence against the gaps in long-term safety data and the regulatory landscape in one's jurisdiction.