GHRP-2
GHRP-2 (pralmorelin) is a synthetic hexapeptide that stimulates growth hormone release by activating the ghrelin receptor. It has been studied in human endocrine testing and is not approved by the FDA.
Overview
GHRP-2, also known by the international nonproprietary name pralmorelin, is one of the synthetic growth hormone-releasing peptides developed in the late 1980s and 1990s, when the receptor they act on had not yet been matched to its natural ligand. The later discovery of ghrelin showed that these peptides mimic the action of this stomach-derived hormone at the growth hormone secretagogue receptor. GHRP-2 was regarded as more potent than GHRP-6 in stimulating growth hormone release in early human studies.
Much of the clinical research on GHRP-2 has focused on its use as a test agent to probe pituitary growth hormone reserve, alone or combined with growth hormone-releasing hormone. It has also been studied in small trials examining appetite, body composition and endocrine responses. As with other GHRPs, it can raise prolactin and cortisol in addition to growth hormone. In the US it is investigational, and it is mainly used as a research tool.
Compare: GHRP-2 vs GHRP-6.
Structure
GHRP-2 is a linear hexapeptide with the sequence D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2, where 2-Nal is the non-natural amino acid 3-(2-naphthyl)alanine. It contains three D-amino acids, which increase resistance to proteolysis, and a C-terminal amide. The tryptophan residue is susceptible to oxidation. Pharmaceutical development used the hydrochloride salt, while research material is commonly supplied as an acetate or trifluoroacetate salt.
Mechanism
GHRP-2 is an agonist of the growth hormone secretagogue receptor type 1a (GHS-R1a), the ghrelin receptor. Activation in the pituitary and hypothalamus stimulates pulsatile growth hormone secretion and acts synergistically with growth hormone-releasing hormone, partly by functionally opposing somatostatin. Ghrelin receptor activation is also linked to increased appetite.
In human studies GHRP-2 has been reported to raise prolactin, adrenocorticotropic hormone and cortisol to a greater extent than more selective agents such as ipamorelin. Responses can be attenuated by repeated exposure and vary with age, body composition and pituitary status.
Research
Diagnostic testing of growth hormone reserve
GHRP-2 has been evaluated as a provocative agent for assessing growth hormone secretion, particularly as a possible alternative to insulin tolerance testing, which carries hypoglycemia risk. Studies compared peak growth hormone responses in healthy volunteers and in people with suspected pituitary disease, and examined combination testing with growth hormone-releasing hormone. This diagnostic use is the most developed clinical application of the peptide.
Endocrine pharmacology
Clinical pharmacology studies characterized the growth hormone response to GHRP-2 across age groups, its synergy with growth hormone-releasing hormone, and its effects on prolactin, cortisol and other hormones. Studies in critically ill patients and in older adults examined how disease and aging alter responses. These studies are generally small and mechanistic rather than outcome trials. Responses in such studies were usually measured over hours after a single exposure.
Appetite and body composition
Because the ghrelin receptor influences hunger, a small number of human studies measured food intake after GHRP-2 administration and reported increases. Animal studies have examined effects on growth, body composition and feeding behavior. These findings are preliminary and do not establish any therapeutic effect on appetite or body composition. Effects on appetite are consistent with the known actions of ghrelin, but they have been measured in only a few small studies.
Evidence quality
The human evidence for GHRP-2 consists mainly of small endocrine and diagnostic studies. There are no large outcome trials, and long-term safety has not been characterized. The compound remains valuable for research on the ghrelin receptor and growth hormone regulation, but it should be regarded as investigational in the US. Its use in sport is prohibited, and anti-doping laboratories have developed methods to detect it.
Regulatory status
GHRP-2 is not approved by the FDA for any use. It is not a recognized substance for US pharmacy compounding. Its regulatory status as a diagnostic agent outside the US should be checked in current national sources. WADA prohibits GHRP-2 and other growth hormone secretagogues under class S2 at all times.
Status changes often. See the regulatory tracker for dated updates.
Quality and identity testing
A certificate of analysis should confirm identity by mass spectrometry against the expected mass shown on this page and report reverse-phase HPLC purity with the chromatogram. The tryptophan residue can oxidize (+16 Da), and this should be monitored. Because three residues are D-amino acids, epimerized impurities with the same mass can be present and require a well-resolved or chiral HPLC method to detect. The counter-ion and net peptide content should be reported.
For a walkthrough of each section of a certificate, see how to read a COA.
Storage and stability
Store lyophilized GHRP-2 sealed at -20 °C or colder, protected from light and moisture; the tryptophan residue makes it sensitive to photo-oxidation. Allow vials to reach room temperature before opening. Solutions for lab use should be prepared in sterile water or buffer, kept refrigerated for short-term work, aliquoted for longer storage at -20 °C or below, and protected from repeated freeze-thaw cycles.
Download the GHRP-2 data sheet (PDF): sequence, masses, expected MS ions and handling on one printable page.
Latest research
The newest PubMed-indexed papers that mention GHRP-2 in their title or abstract, retrieved through Europe PMC and refreshed automatically. Inclusion is not an endorsement of a paper's findings.
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Frequently asked questions
What is the difference between GHRP-2 and GHRP-6?
Both are synthetic hexapeptides that activate the ghrelin receptor. GHRP-2 uses a naphthylalanine residue and an N-terminal D-alanine, while GHRP-6 begins with histidine and uses D-tryptophan. In human studies GHRP-2 was generally more potent for growth hormone release, while GHRP-6 was often described as having a stronger effect on appetite.
Is GHRP-2 FDA approved?
No. GHRP-2 is not approved by the FDA for any use. It has been studied in humans, mainly as a diagnostic test agent for growth hormone secretion and in small endocrine studies. Its status outside the US should be checked in current national regulatory sources.
What is pralmorelin?
Pralmorelin is the international nonproprietary name for GHRP-2. The name is used in pharmaceutical and regulatory contexts, particularly in connection with development of the peptide as a diagnostic agent for testing growth hormone secretion. GHRP-2 and pralmorelin refer to the same hexapeptide.
Related compounds
- GHRP-6
GHRP-6 is a synthetic hexapeptide that stimulates growth hormone release by activating the ghrelin receptor (GHS-R1a). It was one of the first growth hormone secretagogues and is not approved for any use.
- Hexarelin
Hexarelin is a synthetic hexapeptide growth hormone secretagogue that activates the ghrelin receptor. It has been studied in small human studies of growth hormone release and in cardiovascular research, and is not approved for any use.
- Ipamorelin
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue that acts as a selective agonist of the ghrelin receptor (GHS-R1a). It is investigational and not approved for any use.
- CJC-1295
CJC-1295 is a synthetic analogue of growth hormone releasing hormone (GHRH). The name properly refers to a version with a drug affinity complex (DAC) that binds albumin, but is also applied to modified GRF(1-29), which lacks DAC.
References
- PubMed: all indexed literature on GHRP-2
- ClinicalTrials.gov: registered studies mentioning GHRP-2
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