GHRP-6 Peptide

## What it is GHRP-6 is a synthetic hexapeptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) developed in the 1980s by Cyril Bowers' group at Tulane and licensed by SmithKline Beecham as SKF-110679. It was the first synthetic ghrelin-mimetic to demonstrate robust GH release in humans and laid the foundation for the entire GHRP class (including GHRP-2, hexarelin, and ipamorelin) and for the eventual discovery of endogenous ghrelin in 1999. The compound never received FDA, EMA, or PMDA approval as a therapeutic and was not advanced through phase 3 trials in any indication. It is sold today exclusively in the research-peptide grey market and is on the WADA Prohibited List under S2 (peptide hormones, growth factors). The user base is small relative to GHRP-2 and ipamorelin: most body-composition users have migrated to ipamorelin (cleaner side-effect profile) or GHRP-2 (stronger acute GH pulse), leaving GHRP-6 mainly with users specifically chasing appetite stimulation during gaining phases. ## Mechanism of action GHRP-6 binds GHS-R1a, the same receptor activated by endogenous ghrelin and the rest of the GHRP class. The signaling cascade suppresses hypothalamic somatostatin tone and directly stimulates pituitary somatotrophs, producing a pulsatile GH release within 15 to 30 minutes of subcutaneous injection. Like ghrelin, GHRP-6 also engages central NPY/AgRP neurons in the arcuate nucleus, producing the most pronounced hunger response of any synthetic GHRP at equivalent GH-stimulating doses. GHS-R1a activation cross-talks with ACTH and prolactin release; GHRP-6 produces measurable cortisol and prolactin elevation, generally more than ipamorelin and roughly comparable to GHRP-2. Plasma half-life is short, around 15 to 60 minutes, so multi-daily dosing is required for sustained pulse architecture. ## Evidence base The foundational human work comes from Bowers and colleagues across the 1980s and 1990s, demonstrating reproducible GH release after subcutaneous, intravenous, and oral GHRP-6 administration in healthy adults. Penalva 1993 and Micic 1995 documented the GH provocation profile in adult GH deficiency populations, with response patterns similar to GHRP-2 but slightly lower acute peak. No phase 3 RCT exists for GHRP-6 in any indication. Multi-week dosing studies are sparse: a few small trials (n under 30) reported sustained IGF-1 elevation over 2 to 4 weeks of multi-daily dosing, but no body-composition outcomes have been quantified in controlled adult trials. Pediatric short-stature trials in the 1990s reported modest growth velocity gains over 6 months but did not progress to registration. Direct head-to-head data versus GHRP-2 and ipamorelin is limited but consistent: GHRP-6 produces a slightly smaller GH pulse than GHRP-2 at the same molar dose, a substantially larger appetite response than either GHRP-2 or ipamorelin, and a more pronounced cortisol and prolactin profile than ipamorelin. ## Dosage and administration Research-protocol dosing typically runs 100 to 200 mcg subcutaneously 2 to 3 times daily, timed pre-bed, mid-morning, and post-workout to align with endogenous GH pulse windows. The hunger response is dose-related and becomes pronounced above ~150 mcg per injection. Some users specifically pursuing appetite stimulation during gaining phases push to 250 mcg. A typical 5 mg vial reconstituted with 2 mL bacteriostatic water gives 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 for additive GH release via parallel pathways. Anecdotal cycling runs 8 to 12 weeks on, 4 weeks off, with no controlled cycling data. Food intake within 30 to 60 minutes blunts the GH response (circulating glucose and free fatty acids suppress GH). Most protocols call for fasted dosing with a 30 minute window before eating, which conflicts somewhat with the appetite-stimulation use case. ## Side effects and safety The defining subjective effect is intense hunger within 15 minutes of injection, often described as substantially stronger than the GHRP-2 hunger pulse. Other reported effects include water retention, vivid dreams when dosed pre-bed, transient head pressure or flushing, and tingling at the injection site. Cortisol and prolactin elevations are measurable; users with prolactin sensitivity (gynecomastia history, libido changes) sometimes report issues. Long-term safety is not characterized in humans. Theoretical concerns mirror the rest of the GHRP class: insulin resistance with sustained GH elevation (track fasting glucose and HbA1c), theoretical malignancy concern via IGF-1 axis activation, and ACTH-driven cortisol load if dosing is excessive. Pregnancy, active malignancy, history of pituitary tumor, and uncontrolled diabetes are reasonable contraindications. Competitive athletes face WADA sanctions. Detection methods exist for GHRP-6 metabolites in urine. ## Practical notes Lyophilized vials are stable at room temperature; refrigerate 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 provides modest protection against bacterial contamination over the 30-day use period. For most body-composition use cases, GHRP-2 or ipamorelin are now the first-choice GHRPs. GHRP-6 retains a niche where the appetite signal is the desired effect (e.g. underweight gaining phases, post-illness rebuild, eating-disorder recovery contexts under medical supervision). The honest framing is that GHRP-6 is foundational pharmacology with limited modern advantage over its successors, useful primarily when intense hunger is a feature rather than a bug. Measurable IGF-1 elevation typically appears within 2 to 4 weeks of consistent multi-daily dosing. Subjective sleep deepening from pre-bed dosing usually appears within the first week. The hunger pulse is the most reliable subjective effect from dose one. Body-composition changes, if any, accumulate over 8 to 12 weeks and require concurrent training and nutrition for any signal to be detectable above baseline. At the population scale, the GHRP-6 user base has been steadily migrating to ipamorelin since the early 2010s, mirroring the broader pharmacology field's preference for selectivity over potency. The remaining GHRP-6 user community is small and predominantly composed of long-time users with established protocols, plus a smaller wave of users specifically using the appetite signal for therapeutic gaining contexts. If you are starting fresh and unsure which GHRP fits your use case, ipamorelin is the more defensible default; if appetite stimulation is the explicit goal, GHRP-6 retains the strongest signal in the class.