The older-generation GHRPs — GHRP-2 is the pharma-developed version (pralmorelin), GHRP-6 is the hunger-inducing outlier. Both have largely been replaced by ipamorelin in modern protocols.
GHRP-2 (pralmorelin) and GHRP-6 are synthetic hexapeptides developed in the 1980s–1990s as growth hormone secretagogues. Both activate the ghrelin receptor to trigger GH release from the pituitary, but with different secondary profiles:
GHRP-2 was advanced to clinical trials (under the name pralmorelin) in Japan but never fully commercialized. Both are now primarily research chemicals.
Not FDA approved. WADA prohibited (S2). Pralmorelin is still used as a diagnostic agent for GH deficiency in Japan.
Both bind GHS-R1a to trigger GH release. Arvat 1997 (PMID 9285939) gave 6 healthy young adults 1 and 2 mcg/kg IV of each and found GHRP-2 and hexarelin produced a similar GH response — both higher than GHRH (p < 0.05) — so the common ranking that puts hexarelin above GHRP-2 does not come from the human head-to-head. Cheng 1997 (PMID 9096259) showed GHRP-2 and GHRP-6 release GH through the same receptor and the same mechanism in rat pituitary cells despite their structural difference. What separates these compounds is selectivity, not the size of the GH pulse.
GHRP-6 is a stronger functional ghrelin mimetic in the hypothalamic hunger circuit than its peers. Historically used for underweight cachectic patients — now avoided by most users who don’t want the appetite boost.
Read this one carefully, because the usual framing is wrong. In Arvat 1997 (PMID 9285939) GHRP-2 and hexarelin induced similar increases in prolactin, ACTH and cortisol — GHRP-2 is not the gentler of the two. In absolute terms their ACTH/cortisol release was comparable to a hCRH challenge, while prolactin release stayed below TRH. The real contrast is with ipamorelin: Raun 1998 (PMID 9849822) found no ACTH or cortisol rise above GHRH even at more than 200× the dose needed for GH release. That gap, not a difference between GHRP-2 and hexarelin, is why both have lost ground to ipamorelin.
| Benefit | Evidence |
|---|---|
| GH elevation | Both produce reliable GH pulses; Both produce reliable pulses. No human head-to-head has shown GHRP-2 to be the larger of the two; in rat pituitary cells they act through the same receptor and mechanism (Cheng 1997, PMID 9096259) |
| Appetite stimulation | The one effect with a clean human trial behind it. Laferrere 2005 (PMID 15699539) infused GHRP-2 at 1 mcg/kg/h into 7 lean healthy men and food intake at a buffet rose 35.9% versus saline — every subject ate more. GHRP-6 is the stronger hunger stimulus of the two by reputation, but that comparison has not been trialled head-to-head in humans. Useful for hard-gainers; a nuisance otherwise |
| Body composition | No published human data. No trial has measured body composition on either peptide at the doses and schedule used here — the 8–12 week expectation is community pattern extrapolated from GH physiology, not a finding |
| Sleep | Widely reported by users; endogenous GH does peak in slow-wave sleep, but no trial has measured sleep architecture on either peptide |
| Diagnostic use (GHRP-2) | Pralmorelin is approved in Japan as a GH-deficiency diagnostic agent — the one regulatory approval in this family. Doi 2004 (PMID 15646370) is the pharmacological characterisation of KP-102 behind it |
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Start Tracking FreeNot medical advice. These figures describe what is reported in the literature and what practitioners and communities do — not a recommendation, and for most compounds here no human dose-finding study exists. Talk to a qualified healthcare provider.
100 mcg is the commonly cited saturation dose in practitioner protocols — more is reported to produce more side effects rather than a bigger GH pulse. Note that PMID 9285939 tested GHRP-2 at 1–2 mcg/kg IV in adults (~70–140 mcg range) and showed dose-dependent GH responses across that range, so the saturation point is approximate and may vary with body weight. Scale number of pulses per day (up to 3), not per-dose, if you want more total GH exposure.
GHRP + GHRH synergy applies here too. GHRP-2 + CJC-1295 or + sermorelin produces a larger pulse than either alone. Most users who want this stack use ipamorelin instead for the cleaner profile. What does not work is running two GHRPs together: Cheng 1997 (PMID 9096259) found GHRP-2 and GHRP-6 at maximal concentrations produced no more GH than either alone, and desensitised cells to each other while leaving the GHRH response intact. Pair a GHRP with a GHRH analogue, never with another GHRP.
Not medical advice. These figures describe what is reported in the literature and what practitioners and communities do — not a recommendation, and for most compounds here no human dose-finding study exists. Talk to a qualified healthcare provider.
5 mg vial + 2.5 mL BAC water = 2000 mcg/mL
| Dose | Volume | Syringe Units |
|---|---|---|
| 100 mcg | 0.05 mL | 5 units |
| 150 mcg | 0.075 mL | 7.5 units |
Pre-filled with a typical GHRP-2 and GHRP-6 setup. Edit any field — the draw updates live.
Insulin syringe — 100 units = 1 mL
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GHRP-2 and GHRP-6 is a research peptide not approved by the FDA for human use. It is sold only as a research chemical, and StackTrax does not endorse or facilitate personal use.
Quality varies enormously among research-chemical suppliers. At minimum, look for:
Lyvn does not carry GHRP-2 and GHRP-6. They are the vendor we recommend elsewhere on this site, and they publish the full independent panel per batch — which makes their catalogue a useful yardstick for the criteria above even on a compound they do not stock. We are not recommending a specific supplier for GHRP-2 and GHRP-6 itself, because we have no basis to.
For research use only. Not for human consumption. 21+.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeGHRPs are synthetic hexapeptides developed in the 1980s and 1990s as growth hormone secretagogues. They bind the ghrelin receptor (GHS-R1a) on pituitary somatotrophs to trigger a GH pulse — a different pathway from the GHRH receptor that sermorelin/CJC-1295/tesamorelin target. The named GHRP family includes GHRP-2 (pralmorelin), GHRP-6, hexarelin, and ipamorelin. None of them are FDA-approved for hypertrophy or longevity use; all are WADA-prohibited.
All four are ghrelin-receptor agonists that produce a GH pulse, but their secondary profiles differ. The potency ranking usually quoted — hexarelin > GHRP-6 >= GHRP-2 > ipamorelin — is not what the human head-to-head found. In PMID 9285939 GHRP-2 and hexarelin produced a SIMILAR GH response, both higher than GHRH, and similar cortisol and prolactin responses too. And in rat pituitary cells GHRP-2 and GHRP-6 release GH through the same receptor and the same mechanism (PMID 9096259), so the two are closer than the ranking implies. GHRP-6 does have a dramatically stronger hunger response and was historically used as an appetite stimulant. What actually separates these compounds is selectivity, not the size of the GH pulse. Ipamorelin is the cleanest (minimal cortisol/prolactin/hunger), which is why it has largely replaced GHRP-2 and GHRP-6 in modern protocols.
GHRP-6 is a stronger functional ghrelin mimetic in the hypothalamic hunger circuit than its peers. Ghrelin is the bodys hunger hormone, and GHRP-6 mimics that signaling more strongly than GHRP-2 or ipamorelin do. This was historically useful in underweight cachectic patients, but most modern users avoid GHRP-6 specifically because they do not want the appetite boost. GHRP-2 produces modest hunger; ipamorelin essentially none.
Not FDA approved for any indication in the US. WADA prohibited under category S2 (Peptide Hormones, Growth Factors and Related Substances). GHRP-2 (pralmorelin) is approved in Japan as a diagnostic agent for GH deficiency, but is not commercialized as a therapeutic. In the US all GHRPs are sold as research chemicals only.
Community-practice dosing for both GHRP-2 and GHRP-6 is 100–150 mcg subcutaneously, 1–3 times daily, on an empty stomach (more than 2 hours post-meal). 100 mcg is commonly cited as the saturation dose — more reportedly produces more side effects rather than a bigger GH pulse. PMID 9285939 tested GHRP-2 at 1–2 mcg/kg IV in adults (roughly 70–140 mcg) and showed dose-dependent GH responses across that range. To scale total GH exposure, increase the number of pulses per day (up to 3) rather than the per-dose amount.
GHRPs hit the ghrelin receptor; GHRH analogs like CJC-1295 or sermorelin hit the GHRH receptor. Stacking the two stimulates GH release through both pathways simultaneously, producing a larger pulse than either alone. GHRP-2 plus CJC-1295 works, but most users who want the GHRH-plus-GHRP combo now use ipamorelin in place of GHRP-2 because of the cleaner cortisol/prolactin/hunger profile.
Yes — and the usual framing of how much is wrong. PMID 9285939 (Arvat 1997) gave 6 healthy young adults 1 and 2 mcg/kg IV of GHRP-2 and of hexarelin, and found they induced SIMILAR increases in prolactin, ACTH and cortisol. GHRP-2 is not the gentler of the two, even though it is often described that way. In absolute terms their ACTH and cortisol release was comparable to a hCRH challenge, while prolactin release stayed below TRH. The meaningful contrast is with ipamorelin: PMID 9849822 (Raun 1998) found no ACTH or cortisol rise above GHRH even at more than 200 times the dose needed for GH release. That gap is why both GHRP-2 and GHRP-6 have lost ground to ipamorelin.
Disclaimer: This guide is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. The compounds discussed are not FDA approved for human use. Always consult a qualified healthcare provider before starting any new supplement or peptide protocol. StackTrax does not sell peptides or supplements directly — purchase links go to third-party vendors. StackTrax is not responsible for the products, quality, or business practices of any third-party vendor.
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StackTrax guides cover peptides and compounds that are not FDA-approved for the uses discussed. The dosing, reconstitution, and safety information is compiled from published research and community protocols for educational purposes only.
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