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GHRP-2 vs GHRP-6: potency, hunger, cortisol and blends

GHRP-2 and GHRP-6 are synthetic six-amino-acid peptides that release growth hormone through the ghrelin receptor. GHRP-6 came first, in 1984; GHRP-2 is a later analogue that released more growth hormone per microgram in early human work and became a hospital diagnostic test in Japan. Both also raise cortisol and prolactin, both increase appetite in animal studies, and only GHRP-2 has a controlled human study showing people eat more. Neither is approved as a treatment anywhere, and both are banned in sport.

By the PepFinder editorial team · Reviewed 24 Sept 2026 · Editorial independence

GHRP-2 vs GHRP-6: side by side
 GHRP-2GHRP-6
What it isSynthetic hexapeptide, generic name pralmorelin [4]Synthetic hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 [1][12]
First reportedLater analogue; given to people by the early 1990s [3]1984, Bowers and Momany [1]
ReceptorGhrelin receptor (GHS-R1a) [8]Ghrelin receptor (GHS-R1a) [10]
GH releaseThe most effective of the first three GHRPs tested in humans [3]The least effective of the first three GHRPs tested in humans [3]
Potency in pigsHigher potency, lower maximum GH (ED50 0.6 nmol/kg) [6]Lower potency, higher maximum GH (ED50 3.9 nmol/kg) [6]
Cortisol, ACTH, prolactinRaised in healthy adults [7]Prolactin and cortisol about doubled at the highest dose in men [2]
AppetiteHealthy men ate about 36% more in a controlled study [8]Stimulated eating in rats; no controlled human appetite study found [9][10]
Half-life in peopleAbout 33 minutes (0.55 h) after 1 µg/kg IV in children [11]About 2.5 hours after 100 to 400 µg/kg IV in men [12]
ApprovalJapan only, as a single-dose diagnostic for GH deficiency [4][5]Never approved
Doses used in studies100 µg IV (diagnostic test); 1 µg/kg IV; 1 µg/kg per hour infusion [5][8][11]0.1 to 1.0 µg/kg IV; 90 µg IV with GHRH in a diagnostic test [2][16]
WADAProhibited at all times, named as GHRP-2 (pralmorelin) [20]Prohibited at all times, named as GHRP-6 [20]
Full guideGHRP-2 guideGHRP-6 guide

GHRP-2 vs GHRP-6: the short answer

Both peptides do the same basic thing: they bind the ghrelin receptor in the pituitary and hypothalamus and trigger a pulse of growth hormone (GH). The differences are of degree and of history. GHRP-6 is the original compound. GHRP-2 came later and, in human testing reported by Bowers, released GH more effectively [3]. GHRP-2 is also the one that reached a regulator: Japan approved it, as pralmorelin, for a single-dose diagnostic test [4][5].

Neither is selective for GH. Both raise ACTH and cortisol, and both raise prolactin to some degree [2][6][7]. Both are described as increasing hunger, but the only controlled human appetite study is of GHRP-2 [8]. Our full GHRP-2 guide and GHRP-6 guide cover each one separately.

Difference between GHRP 2 and 6: where they came from

GHRP-6 was reported in 1984 by Cyril Bowers and Frank Momany as a small synthetic peptide that released GH specifically in rats, monkeys, lambs and calves, before anyone knew which receptor it acted on [1]. That receptor was cloned in 1996 [28] and its natural hormone, ghrelin, was identified in 1999 [29], so GHRP-6 is the parent of a family that includes GHRP-2, hexarelin and ipamorelin.

GHRP-2 followed as one of the second-generation compounds. A 1993 review by Bowers reported that three GHRPs had then been given to people, GHRP-6, GHRP-1 and GHRP-2, and that they were increasingly effective at releasing GH in that order, as they had been in rats [3]. A 1997 Italian study described GHRP-2 and hexarelin as super-analogues of GHRP-6 [7].

Which releases more growth hormone?

In people, GHRP-2 is generally described as the stronger releaser [3]. In a Japanese validation study, a single 100 µg intravenous dose of GHRP-2 gave healthy adults a mean peak GH of 84.6 µg/L, which is why it works as a diagnostic stimulus [5]. For GHRP-6, intravenous doses of 0.1, 0.3 and 1.0 µg/kg in 18 healthy men produced mean peaks of 7.6, 16.5 and 68.7 µg/L [2]. These studies used different doses, people and assays, so the numbers cannot be compared directly.

The one side-by-side animal comparison adds a nuance. In conscious pigs, GHRP-2 was more potent than GHRP-6 (it needed a smaller dose for half its maximum effect, 0.6 against 3.9 nmol/kg), but its maximum GH response was lower (56 against 74 ng/mL) [6]. More potent does not necessarily mean a bigger peak.

Cortisol, ACTH and prolactin

Neither peptide releases GH alone. In the pig study, both GHRP-2 and GHRP-6 raised ACTH and cortisol, whereas ipamorelin did not [6]. In six healthy young adults, GHRP-2 at 1 and 2 µg/kg intravenously raised prolactin, ACTH and cortisol, with the ACTH and cortisol rises similar in size to those after the stress-hormone releaser CRH [7]. For GHRP-6, the 1990 dose-ranging study in men found that prolactin and cortisol each rose about twofold at the highest dose [2].

A 2026 clinical review of GH-axis peptides lists prolactin and cortisol rises among the adverse effects reported with GH secretagogues as a class [24]. We found no human study that measured cortisol or prolactin after GHRP-2 and GHRP-6 in the same people.

GHRP-6 hunger vs GHRP-2 hunger

GHRP-6 is widely described as the peptide that makes people very hungry. The laboratory evidence is real but comes from animals. In sated adult rats, GHRP-6 injected into the brain’s ventricles stimulated eating in a nearly linear, dose-dependent way, without a matching change in blood GH, so the authors concluded the feeding effect was separate from GH release [9]. A later rat study found GHRP-6 activated appetite centres in the hypothalamus and brainstem and that its effect on food intake was blocked by a neuropeptide Y receptor antagonist [10]. In mice, two weeks of GHRP-6 or ipamorelin increased relative body fat, which the authors linked to increased feeding [26].

For GHRP-2 there is human evidence. Seven lean, healthy men given a subcutaneous infusion of GHRP-2 at 1 µg/kg per hour for 270 minutes ate 35.9% more at a buffet meal than after saline, and every one of them ate more [8]. In children with GH deficiency given oral GHRP-2 for a year, seven of ten reported increased appetite in the first six months [25].

So the common claim that GHRP-6 causes more hunger than GHRP-2 has not been tested. No human study has compared their effects on appetite, and we found no controlled human appetite study of GHRP-6 at all. What can be said is that both act on the receptor that ghrelin, the hunger hormone, uses, and that appetite has been measured and confirmed in people only for GHRP-2.

Half-life, routes and detection

In ten children given a single 1 µg/kg intravenous dose, GHRP-2 had an elimination half-life of 0.55 hours, about 33 minutes [11]. In nine healthy men given much larger intravenous doses of GHRP-6, from 100 to 400 µg/kg, the elimination half-life averaged about 2.5 hours, and four volunteers showed unexplained concentration spikes during elimination [12]. The doses, ages and assays differ, so this is not a clean comparison of the two molecules.

Both work by several routes. The 1993 review reported GH release after intravenous, subcutaneous and oral dosing of all three early GHRPs, with near-maximal GH after oral GHRP-1 and GHRP-2 [3]. An anti-doping study gave each peptide by nasal spray to one volunteer: GHRP-2 and its metabolites were detectable in urine for up to 47 hours, while GHRP-6 was excreted mostly unchanged and detected for 23 hours [19].

Doses used in published research

These are the doses researchers used, listed as information, not recommendations. For GHRP-2: a single 100 µg intravenous dose in the Japanese diagnostic test [5]; a single 1 µg/kg intravenous dose in children [11]; a subcutaneous infusion of 1 µg/kg per hour in the appetite study [8]; and continuous subcutaneous infusion at 1 µg/kg per hour for 30 days in older adults, which kept GH and IGF-1 raised with normal safety screening tests [14].

For GHRP-6: single intravenous doses of 0.1 to 1.0 µg/kg in healthy men [2]; 90 µg intravenously together with 90 µg of GHRH in a diagnostic test that proved reproducible over six months [16]; and 100 to 400 µg/kg intravenously in the pharmacokinetic study [12]. For converting a vial’s milligrams into micrograms per unit, see our peptide calculator.

GHRP-2 and GHRP-6 together

The only published human data on the two together come from a US men’s health clinic. A retrospective review found 105 men on testosterone therapy who had been prescribed 100 µg each of GHRP-6, GHRP-2 and sermorelin three times daily. Only 14 met the strict compliance criteria for analysis. Over an average of 134 days, their mean IGF-1 rose from 159.5 to 239.0 ng/mL [15]. There was no control group, and the design cannot separate the effect of each peptide.

Because both bind the same receptor, there is no mechanistic reason to expect them to add to each other the way a GHRP and a GHRH do. No study has tested GHRP-2 plus GHRP-6 against either alone.

Blends with Mod GRF 1-29 and CJC-1295

Much of the search interest here is in pre-mixed vials: people look for “Mod GRF 1-29 & GHRP-2 blend”, “Mod GRF 1-29 & GHRP-6 blend”, “CJC-1295 & GHRP-2 blend” and “CJC-1295 & GHRP-6”, often at 10mg. The idea behind them is established pharmacology. GHRPs and GHRH act through different receptors, and in healthy men GHRP-6 combined with GHRH released more GH than the two would be expected to release separately [2]. The same synergy has been shown for GHRP-2: in older adults a 24-hour infusion of GHRP-2 with GHRH drove GH secretion more than either alone [14], and in critically ill patients GHRH plus GHRP-2 doubled mean GH compared with GHRP-2 alone and raised IGF-1 by a further 40% [13]. How large the synergy is varies with age, abdominal fat and IGF-1 levels [17].

Those studies used natural GHRH or GHRH(1-29), not the products in the vials. Mod GRF 1-29, sold as “CJC-1295 no DAC”, is a modified GRF(1-29) with no published human studies of its own; the human data for CJC-1295 come from the long-acting DAC version, which had a half-life of about six to eight days [18]. We found no published study of Mod GRF 1-29 or CJC-1295 combined with GHRP-2 or GHRP-6. Anti-doping laboratories have found glycine-modified versions of both Mod GRF 1-29 and GHRPs in seized products [21], which is one reason the label on a blend cannot be taken on trust.

The supplier listings we track do not include enough GHRP blends for us to describe a typical composition, so we do not give one. See our CJC-1295 guide for the difference between the DAC and no-DAC molecules, and CJC-1295 prices for what is on sale.

Side effects reported

In the published human studies, the effects of both peptides are mainly hormonal: GH rises, along with cortisol, ACTH and prolactin [2][7], and appetite increases with GHRP-2 [8][25]. In the 1990 GHRP-6 study no adverse clinical effects or laboratory abnormalities were seen after injection [2]. In the 30-day GHRP-2 infusion study in older adults, safety screening tests stayed normal [14].

These studies were short and small. GHRP-2’s use as a one-off diagnostic in Japan says nothing about repeated use, and there are no long-term safety data for either peptide. The 2026 review of GH-axis peptides lists appetite changes, altered glucose, fluid retention, joint and muscle pain and injection-site reactions among the effects reported with this group [24].

Prices and testing

You can compare GHRP-2 prices and GHRP-6 prices per milligram across the suppliers we track. Because glycine-modified analogues have turned up in seized material, a certificate of analysis that confirms identity by mass matters more than a purity figure alone; our guide on how to read a peptide COA explains what to check, and our list of suppliers with published COAs shows who makes theirs available. Storage guidance is in our peptide storage guide.

Full guides and prices

References

  1. [1] Bowers CY, Momany FA, Reynolds GA, Hong A On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone Endocrinology. 1984. PubMed 6714155
  2. [2] Bowers CY, Reynolds GA, Durham D, Barrera CM, et al. Growth hormone (GH)-releasing peptide stimulates GH release in normal men and acts synergistically with GH-releasing hormone J Clin Endocrinol Metab. 1990. PubMed 2108187
  3. [3] Bowers CY GH releasing peptides: structure and kinetics J Pediatr Endocrinol. 1993. PubMed 8374685
  4. [4] Kanehisa Laboratories KEGG DRUG D02040: Pralmorelin dihydrochloride (USAN); pralmorelin hydrochloride (JAN); GHRP (TN) KEGG DRUG database. 2026. Source
  5. [5] Chihara K, Shimatsu A, Hizuka N, Tanaka T, et al. A simple diagnostic test using GH-releasing peptide-2 in adult GH deficiency Eur J Endocrinol. 2007. PubMed 17609397
  6. [6] Raun K, Hansen BS, Johansen NL, Thøgersen H, et al. Ipamorelin, the first selective growth hormone secretagogue Eur J Endocrinol. 1998. PubMed 9849822
  7. [7] Arvat E, di Vito L, Maccagno B, Broglio F, et al. Effects of GHRP-2 and hexarelin, two synthetic GH-releasing peptides, on GH, prolactin, ACTH and cortisol levels in man. Comparison with the effects of GHRH, TRH and hCRH Peptides. 1997. PubMed 9285939
  8. [8] Laferrère B, Abraham C, Russell CD, Bowers CY Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men J Clin Endocrinol Metab. 2005. PubMed 15699539
  9. [9] Locke W, Kirgis HD, Bowers CY, Abdoh AA Intracerebroventricular growth-hormone-releasing peptide-6 stimulates eating without affecting plasma growth hormone responses in rats Life Sciences. 1995. PubMed 8614257
  10. [10] Lawrence CB, Snape AC, Baudoin FM, Luckman SM Acute central ghrelin and GH secretagogues induce feeding and activate brain appetite centers Endocrinology. 2002. PubMed 11751604
  11. [11] Pihoker C, Kearns GL, French D, Bowers CY Pharmacokinetics and pharmacodynamics of growth hormone-releasing peptide-2: a phase I study in children J Clin Endocrinol Metab. 1998. PubMed 9543135
  12. [12] Cabrales A, Gil J, Fernández E, Valenzuela C, et al. Pharmacokinetic study of growth hormone-releasing peptide 6 (GHRP-6) in nine male healthy volunteers Eur J Pharm Sci. 2013. PubMed 23099431
  13. [13] Van den Berghe G, de Zegher F, Veldhuis JD, Wouters P, et al. The somatotropic axis in critical illness: effect of continuous growth hormone (GH)-releasing hormone and GH-releasing peptide-2 infusion J Clin Endocrinol Metab. 1997. PubMed 9024260
  14. [14] Bowers CY, Granda R, Mohan S, Kuipers J, et al. Sustained elevation of pulsatile growth hormone (GH) secretion and insulin-like growth factor I (IGF-I), IGF-binding protein-3 (IGFBP-3), and IGFBP-5 concentrations during 30-day continuous subcutaneous infusion of GH-releasing peptide-2 in older men and women J Clin Endocrinol Metab. 2004. PubMed 15126555
  15. [15] Sigalos JT, Pastuszak AW, Allison A, Ohlander SJ, et al. Growth hormone secretagogue treatment in hypogonadal men raises serum insulin-like growth factor-1 levels Am J Mens Health. 2017. PubMed 28830317
  16. [16] Popovic V, Pekic S, Simic M, Damjanovic S, et al. Physical activity or food intake prior to testing did not affect the reproducibility of GH secretion elicited by GH releasing hormone plus GH-releasing hexapeptide in normal adult subjects Clin Endocrinol (Oxf). 2002. PubMed 11849251
  17. [17] Veldhuis JD, Bowers CY Determinants of GH-releasing hormone and GH-releasing peptide synergy in men Am J Physiol Endocrinol Metab. 2009. PubMed 19240251
  18. [18] Teichman SL, Neale A, Lawrence B, Gagnon C, et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults J Clin Endocrinol Metab. 2006. PubMed 16352683
  19. [19] Semenistaya E, Zvereva I, Thomas A, Thevis M, et al. Determination of growth hormone releasing peptides metabolites in human urine after nasal administration of GHRP-1, GHRP-2, GHRP-6, Hexarelin, and Ipamorelin Drug Test Anal. 2015. PubMed 25869809
  20. [20] World Anti-Doping Agency The Prohibited List (2026): S2.2.4 Growth hormone releasing factors wada-ama.org. 2026. Source
  21. [21] Gajda PM, Holm NB, Hoej LJ, Rasmussen BS, et al. Glycine-modified growth hormone secretagogues identified in seized doping material Drug Test Anal. 2019. PubMed 30136411
  22. [22] US Food and Drug Administration Certain bulk drug substances for use in compounding that may present significant safety risks FDA. 2026. Source
  23. [23] Australian Government Therapeutic Goods (Poisons Standard—June 2026) Instrument 2026 Federal Register of Legislation. 2026. Source
  24. [24] Dominikowski A, Rękoś Z, Olejarz M, Szczepanek-Parulska E, et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration Front Endocrinol (Lausanne). 2026. PubMed 42395176
  25. [25] Mericq V, Cassorla F, Bowers CY, Avila A, et al. Changes in appetite and body weight in response to long-term oral administration of the ghrelin agonist GHRP-2 in growth hormone deficient children J Pediatr Endocrinol Metab. 2003. PubMed 14513874
  26. [26] Lall S, Tung LY, Ohlsson C, Jansson JO, Dickson SL Growth hormone (GH)-independent stimulation of adiposity by GH secretagogues Biochem Biophys Res Commun. 2001. PubMed 11162489
  27. [27] Medsafe, New Zealand Ministry of Health Medicines classification database medsafe.govt.nz. 2026. Source
  28. [28] Howard AD, Feighner SD, Cully DF, Arena JP, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release Science. 1996. PubMed 8688086
  29. [29] Kojima M, Hosoda H, Date Y, Nakazato M, et al. Ghrelin is a growth-hormone-releasing acylated peptide from stomach Nature. 1999. PubMed 10604470

Frequently asked questions

GHRP 2 vs 6: which is stronger?

In early human work GHRP-2 released growth hormone more effectively than GHRP-6. In pigs GHRP-2 was more potent but produced a lower maximum GH response. No modern head-to-head human trial exists.

What is the difference between GHRP 2 and 6?

Both are synthetic ghrelin-receptor agonists from the same research programme. GHRP-6 was first, in 1984; GHRP-2 came later, released more GH per dose in human studies, and is approved in Japan as a diagnostic test.

Does GHRP-6 make you hungrier than GHRP-2?

That is widely claimed but has not been tested. GHRP-6 stimulated eating in rats, while GHRP-2 is the only one with a controlled human study, in which men ate about 36% more. No study has compared the two for appetite.

GHRP 6 vs GHRP 2: which raises cortisol more?

Both raise cortisol, ACTH and prolactin. No study has measured them in the same people, so there is no evidence that one raises cortisol more than the other.

Can you take GHRP-2 and GHRP-6 together?

The only published human data come from a small retrospective clinic review of men prescribed GHRP-2, GHRP-6 and sermorelin together, with no control group. Both peptides act on the same receptor.

Why are GHRPs combined with Mod GRF 1-29 or CJC-1295?

Because GHRPs and GHRH act on different receptors, and human studies show the two together release more GH than either alone. Those studies used natural GHRH; no study has tested Mod GRF 1-29 or CJC-1295 with a GHRP.

What is the half-life of GHRP-2 and GHRP-6?

About 33 minutes for GHRP-2 after a small intravenous dose in children, and about 2.5 hours for GHRP-6 after large intravenous doses in men. The studies differed too much for a direct comparison.

Is GHRP-2 or GHRP-6 approved by the FDA?

No. Neither is FDA-approved, and the FDA lists both among compounding substances that may present significant safety risks. GHRP-2 is approved only in Japan, as a diagnostic test.

Are GHRP-2 and GHRP-6 banned in sport?

Yes. Both are named on the WADA Prohibited List as GH-releasing peptides and are banned at all times.

Sermorelin and GHRP-6: has the combination been studied?

GHRP-6 with natural GHRH showed synergy in healthy men, and sermorelin is the active 29-amino-acid fragment of GHRH. Sermorelin with GHRP-6 specifically appears only in the retrospective clinic review, alongside GHRP-2.

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