What is GHRP-2?
GHRP-2 (growth hormone releasing peptide 2) is a synthetic hexapeptide that releases growth hormone (GH). Its international nonproprietary name is pralmorelin, and its Japanese developer coded it KP-102 (Doi et al., 2004). It came from Cyril Bowers' program at Tulane University, where GHRP-6, GHRP-1 and GHRP-2 proved increasingly effective GH releasers in people, more efficacious than GHRH and active by mouth (Bowers, 1993).
GHRP-2 is an agonist of GHS-R1a, the growth hormone secretagogue receptor (Yamamoto et al., 2008), which the gut hormone ghrelin also binds (Laferrère et al., 2005). A 2016 review of ghrelin receptor ligands in clinical trials found that only GHRP-2 had reached the market, through approval in Japan for diagnostic purposes (Vodnik et al., 2016). Disguised Alpha does not currently list GHRP-2; this page is a literature reference for laboratory researchers. Nothing on this page is guidance for use in people.
GHRP-2 reference data
| Property | Value |
|---|---|
| Name | GHRP-2 (growth hormone releasing peptide 2) |
| Also called | Pralmorelin (INN), GHRP 2, KP-102, GPA-748; the dihydrochloride salt is pralmorelin hydrochloride (PubChem CID 9940988) |
| Sequence | D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2: six residues, three of them D-amino acids and one non-standard (2-naphthylalanine), with a C-terminal amide |
| Compound class | Synthetic hexapeptide growth hormone secretagogue; GHS-R1a (ghrelin receptor) agonist |
| Molecular formula | C₄₅H₅₅N₉O₆ (free base) |
| Molecular weight | 818.0 g/mol (free base); 890.9 g/mol as the dihydrochloride |
All values are from PubChem: CID 6918245 for the free base (pralmorelin) and CID 9940988 for the dihydrochloride. The developer's KP-102 pharmacology paper labels the dihydrochloride with the registry number that PubChem files under the free base (Doi et al., 2004).
See it beside the other compounds on this site in the peptide molecular weight reference table.
What the research covers
Published work on GHRP-2 falls into five areas, each summarized below with its model.
Receptor pharmacology
In rat pituitary cells, GHRP-2 and GHRP-6 were not additive at maximal concentrations and desensitized the cells to each other but not to GHRH, and a peptide antagonist inhibited GHRP-2 while a GHRH antagonist did not; the authors concluded that both use the same receptor, and GHRP-2 was synergistic with GHRH (Cheng et al., 1997).
In membranes from human pituitary and hypothalamus, GHRP-2 displaced a radiolabeled secretagogue from specific binding sites, as did hexarelin, GHRP-6 and the non-peptide MK-0677, while GHRH and somatostatin did not (Muccioli et al., 1998). GHRP-2 also acts through GHS-R1a outside the pituitary: in differentiated C2C12 muscle cells it lowered dexamethasone-induced expression of the ubiquitin ligases atrogin-1 and MuRF1, and the GHS-R1a blocker [D-Lys3]-GHRP-6 prevented the effect (Yamamoto et al., 2008). Models: rat pituitary cells, human pituitary and brain membranes, mouse C2C12 cells.
GH release in animals and the role of GHRH
In conscious rats, GHRP-2 was more potent than exogenous GHRH, and in conscious dogs it raised GH where GHRH failed. Its effect was absent in hypophysectomized rats and smaller in rats with median eminence lesions, indicating that the full response needs endogenous GHRH; in cultured rat pituitary cells it was weaker than GHRH (Doi et al., 2004).
In GHRH knockout mice, six weeks of GHRP-2 did not stimulate somatotroph proliferation, GH secretion or longitudinal growth (Alba et al., 2005). In conscious swine, GHRP-2 was more potent than ipamorelin and GHRP-6 (ED50 0.6 nmol/kg) but reached a lower GH maximum (Raun et al., 1998). Models: rats, dogs, knockout mice and swine.
ACTH, cortisol and prolactin
GHRP-2 is not selective for GH. In six healthy young adults, intravenous GHRP-2 and hexarelin gave similar strong GH responses, above those to GHRH, and they raised prolactin, though less than TRH did, and ACTH and cortisol about as much as human CRH did (Arvat et al., 1997). Species differ: prolactin did not rise in conscious rats (Doi et al., 2004) or in swine, where GHRP-2 and GHRP-6, unlike ipamorelin, raised ACTH and cortisol (Raun et al., 1998).
In rats, GHRP-2 did not release ACTH from cultured pituitary cells, and a CRF antagonist, not an AVP antagonist, markedly blocked its ACTH response in vivo; the authors placed the effect in the hypothalamus, mainly through CRF (Hirotani et al., 2005). Models: healthy adults, rats, swine and rat pituitary cells.
Diagnostic testing in people
A 2004 drug profile reported that the diagnostic form awaited approval in Japan and that US phase II development for GH deficiency appeared to have been discontinued (Drugs R D, 2004). In a validation study by Japan's KP-102 Study Group, 77 healthy adults and 58 adults with severe GH deficiency confirmed by the insulin tolerance test had an intravenous GHRP-2 test.
Mean peak GH, reached within 60 minutes, was 84.6 µg/l in the healthy group and 1.36 µg/l in the deficient group, and a 15 µg/l cutoff matched the insulin tolerance test's 3 µg/l criterion; responses were reproducible and only slightly lower with older age and adiposity (Chihara et al., 2007). Models: healthy adults and adults with hypothalamic or pituitary disease.
Repeated exposure, appetite and critical illness
GH responses can attenuate: in nine healthy young men given GHRP-2 once daily for five days, mean peak GH fell from 83 µg/l on day 1 to 51 µg/l on day 5, and IGF-I did not rise (Nijland et al., 1998). Like ghrelin, GHRP-2 raised food intake: after a subcutaneous GHRP-2 infusion, each of seven lean, healthy men ate more at a buffet meal than after saline, 35.9 percent more on average (Laferrère et al., 2005).
In a randomized crossover study of 26 critically ill adults, GHRP-2 infusion raised mean GH 4 to 6 fold and IGF-I by 61 percent within 24 hours, and the elevated cortisol did not change (Van den Berghe et al., 1997). In a 48-week double-blind trial in 126 prepubertal children with GH deficiency, placebo and two amounts of an intranasal GHRP-2 spray produced similar changes in height SD score and IGF-I (Tanaka et al., 2014). Models: healthy men, critically ill adults and children with GH deficiency.
Key studies
- Cheng J, et al. "Growth hormone releasing peptides: a comparison of the growth hormone releasing activities of GHRP-2 and GHRP-6 in rat primary pituitary cells." Life Sci. 1997. PMID 9096259. DOI 10.1016/s0024-3205(96)00655-8. Rat pituitary cells, desensitization and antagonist tests: a receptor shared with GHRP-6.
- Arvat E, 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. PMID 9285939. DOI 10.1016/s0196-9781(97)00016-8. Six healthy young adults: prolactin, ACTH and cortisol rose with GH.
- Raun K, et al. "Ipamorelin, the first selective growth hormone secretagogue." Eur J Endocrinol. 1998. PMID 9849822. DOI 10.1530/eje.0.1390552. Conscious swine: GHRP-2 and GHRP-6, not ipamorelin, raised ACTH and cortisol.
- Doi N, et al. "Pharmacological characteristics of KP-102 (GHRP-2), a potent growth hormone-releasing peptide." Arzneimittelforschung. 2004. PMID 15646370. DOI 10.1055/s-0031-1297041. Rats, dogs and pituitary cells: full GH release needs the pituitary and endogenous GHRH.
- Chihara K, et al. "A simple diagnostic test using GH-releasing peptide-2 in adult GH deficiency." Eur J Endocrinol. 2007. PMID 17609397. DOI 10.1530/EJE-07-0066. 77 healthy and 58 GH-deficient adults: a 15 µg/l peak GH cutoff.
Handling and storage of lyophilized GHRP-2
General laboratory practice for a lyophilized peptide, in line with the site's peptide storage guide and reconstitution guide:
- Keep the sealed powder at -20°C, dry and dark; tryptophan and phenylalanine are prone to photo-oxidation.
- Let a cold vial reach room temperature before opening so moisture does not condense on the powder.
- Choose the diluent from your protocol. The sequence has two basic amines, no acidic residues and three large aromatic side chains; follow the reconstitution guide's solubility rules and test a small portion first.
- Add diluent down the vial wall and swirl gently; do not shake or vortex.
- Keep solutions at 2 to 8°C, dark, in single-use aliquots, without freeze/thaw cycles; dilute cationic peptides can adsorb to container walls.
- Check whether a certificate reports the free base (818.0 g/mol) or a salt before calculating molarity.
Frequently asked questions
What is GHRP-2?
GHRP-2, or pralmorelin, is a synthetic hexapeptide from the GHRP family that includes GHRP-6 and GHRP-1 (Bowers, 1993). It is an agonist of GHS-R1a, the growth hormone secretagogue (ghrelin) receptor (Yamamoto et al., 2008).
Is GHRP-2 a peptide?
Yes. The GHRP-2 peptide is a hexapeptide, six amino acids joined by peptide bonds and capped with a C-terminal amide. Three residues are D-amino acids and one, 2-naphthylalanine, is not found in proteins; one paper calls it a synthetic, non-natural super-analog of GHRP-6 (Arvat et al., 1997).
Is pralmorelin the same as GHRP-2?
Yes. Pralmorelin is the international nonproprietary name for GHRP-2, and KP-102 is its Japanese development code (Hirotani et al., 2005); PubChem lists all three under CID 6918245.
How does GHRP-2 compare with ipamorelin?
Both act at the secretagogue receptor, but in swine GHRP-2 raised ACTH and cortisol, while ipamorelin, a pentapeptide, did not raise them beyond the levels seen with GHRH (Raun et al., 1998). See the ipamorelin research guide.
Has GHRP-2 been studied in people?
Yes, as research history in healthy volunteers, critically ill adults, children with GH deficiency and adults with hypothalamic or pituitary disease. Japan approved it for diagnostic purposes (Vodnik et al., 2016); US development appeared to have been discontinued by 2004 (Drugs R D, 2004). An FDA page on bulk drug substances that may present significant safety risks has listed GHRP-2, for injectable and nasal routes, in 503B category 2 since September 29, 2023.
It says compounded GHRP-2 for those routes may pose a risk of immunogenicity due to the potential for aggregation and peptide-related impurities, and that FDA is aware of reports of serious adverse events in patients who received GHRP-2, including increased insulin requirement to maintain the blood glucose level, death of critically ill study subjects, infection and pancreatitis, though causality has not been established.
Is GHRP-2 on the WADA Prohibited List?
Yes. The 2026 World Anti-Doping Agency Prohibited List names GHRP-2 (pralmorelin) among GH-releasing peptides in S2.2.4, growth hormone releasing factors. Class S2 is prohibited at all times.
Does Disguised Alpha sell GHRP-2?
Not currently. Related catalog compounds with research guides: ipamorelin, a pentapeptide GH secretagogue, and MK-677, a non-peptide GH secretagogue.
Related compounds and guides
- Growth hormone secretagogues explained
- Ipamorelin research guide
- MK-677 research guide
- Peptide storage guide
- How to reconstitute peptides in the lab
- Lyophilized peptides explained
Literature reference for laboratory research only.