GHRP-2 Peptide

## What it is GHRP-2 is a synthetic hexapeptide growth-hormone secretagogue developed in the 1990s by Wyeth-Ayerst and licensed in Japan as pralmorelin (Kaken Pharmaceutical) for use as a diagnostic agent in suspected adult growth-hormone deficiency. The peptide sequence (D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2) was engineered for resistance to enzymatic cleavage and selective binding at the growth-hormone secretagogue receptor (GHS-R1a), the same receptor activated by endogenous ghrelin. It is not approved by the FDA, EMA, or any major Western regulator as a therapeutic. Pralmorelin received Japanese approval as a diagnostic provocation test (administered intranasally or intravenously to provoke a measurable GH response) and remains in limited clinical use there. In the rest of the world it is sold strictly through research-peptide vendors and falls outside the supplement and prescription drug frameworks. WADA places GHRP-2 on the Prohibited List under S2 (peptide hormones and growth factors) and detection methods are validated for accredited anti-doping labs. The user base is split between body-composition focused athletes pairing it with a GHRH analog like CJC-1295 or sermorelin, and a smaller group using it as an appetite stimulant during gaining phases. The hunger response is the most reliable subjective effect, often appearing within 15 minutes of injection. ## Mechanism of action GHRP-2 binds GHS-R1a with high affinity, mimicking ghrelin's stimulus on hypothalamic neurons (which suppress somatostatin) and pituitary somatotrophs (which release GH). The dual action is why GHRPs are typically combined with GHRH analogs in research protocols: GHRH directly stimulates GH synthesis at the somatotroph, while GHRP simultaneously suppresses the somatostatin brake. The combined pulse is substantially larger than either pathway alone in healthy adult studies. GHS-R1a activation also stimulates ACTH and prolactin release through cross-talk in the hypothalamic-pituitary axis. GHRP-2 produces a more pronounced cortisol and prolactin rise than ipamorelin (which is far more selective for GH release) but a less pronounced one than GHRP-6. The effect on appetite operates centrally through arcuate nucleus NPY/AgRP neurons, the same circuit ghrelin uses to drive food intake. Plasma half-life is short, on the order of 15 to 60 minutes depending on route. Subcutaneous injection produces a GH peak within 15 to 30 minutes that returns to baseline within 2 to 3 hours. Intranasal administration was the clinical Japanese route for diagnostic use; bioavailability via that route is roughly 0.3 to 1%. ## Evidence base The most rigorous human data comes from the diagnostic literature. Bowers and colleagues characterized GH responses to GHRP-2 across pediatric and adult populations through the 1990s, and Chihara 2007 and Mukai 1999 documented diagnostic performance for adult GH deficiency in Japanese clinical trials with several hundred participants combined. The provocation test is well-validated for distinguishing GH-deficient from healthy adults at a 100 mcg intravenous or 200 to 400 mcg/kg intranasal dose. Long-term efficacy in chronic dosing scenarios (the pattern relevant to body-composition users) has not been studied in completed phase 3 trials. Bowers 2001 reported sustained GH and IGF-1 elevation during multiple-dose protocols over weeks but small sample sizes (under 30 per arm) limit translation. A pediatric idiopathic short stature trial (Mericq 1998) showed modest growth velocity increases over 6 months but did not progress to a registration trial. No body-composition outcomes have been quantified in controlled adult trials. Direct comparisons between GHRP-2, GHRP-6, hexarelin, and ipamorelin show GHRP-2 produces the largest acute GH pulse but a less favorable selectivity profile than ipamorelin (more cortisol and prolactin release) and a less pronounced appetite effect than GHRP-6. ## Dosage and administration Research-protocol dosing typically runs 100 to 300 mcg subcutaneously 2 to 3 times daily, timed to align with endogenous GH pulse windows: pre-bed, mid-morning, and post-workout are the conventional triad. Most anecdotal users dose 100 mcg per injection, while those pursuing maximum acute response push to 200 to 300 mcg with diminishing returns above 1 mcg/kg. A typical 5 mg vial reconstituted with 2 mL bacteriostatic water yields 2.5 mg/mL. A 100 mcg dose draws 4 units on a U100 insulin syringe. The peptide is commonly stacked with CJC-1295 no-DAC (Mod GRF 1-29) at the same time point on the rationale of synergistic GH release. Anecdotal cycle structure is 8 to 12 weeks on, 4 weeks off, with no controlled data behind the cadence. Food intake within 30 to 60 minutes before or after injection blunts the GH pulse, since circulating glucose and free fatty acids suppress GH release. Most protocols call for a fasted state at injection and a 30 minute window before eating. ## Side effects and safety The most reliable subjective effect is acute hunger within 15 minutes of injection, followed by a head-pressure or mild flush sensation. Other reported effects include water retention, vivid dreams when dosed pre-bed, transient lethargy, and tingling at the injection site. Cortisol and prolactin elevations are real but typically modest at standard doses; users sensitive to prolactin (gynecomastia history, libido sensitivity) sometimes report issues. Long-term safety is not characterized in humans. Theoretical concerns include the same insulin resistance pattern seen with sustained GH elevation (track fasting glucose and HbA1c in extended use), accelerated growth of occult malignancy via IGF-1 axis activation, and ACTH-driven cortisol elevation if dosing is excessive. Pregnancy, active malignancy, history of pituitary tumor, and uncontrolled diabetes are reasonable contraindications on mechanistic grounds. Competitive athletes face WADA sanctions. Detection methods are validated and several published cases involve GHRP-2 metabolites in athlete urine. ## Practical notes Lyophilized vials are stable at room temperature for the labeled shelf life and should be refrigerated for longer storage. Reconstituted vials should be refrigerated and used within 4 weeks. Bacteriostatic water (not sterile water) is the standard reconstitution medium because the benzyl alcohol preservative resists bacterial contamination over the use period. Expect the hunger pulse and head-pressure feel within the first dose. Subjective sleep deepening, when present, typically appears in week 1 to 2 of consistent pre-bed dosing. IGF-1 elevation becomes measurable in serum after roughly 2 to 4 weeks of consistent multi-daily dosing; if a baseline and follow-up labs show no IGF-1 movement, the vial is most likely under-dosed or inactive, a recurring problem in unregulated supply chains. The honest framing is that GHRP-2 has well-characterized acute pharmacology, sparse chronic-use data, and is being deployed by a population that has decided the asymmetric bet works for them.