Quick answer: GHRP-2 (pralmorelin) is a synthetic hexapeptide, D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2, that belongs to the growth hormone-releasing peptide family. It was built from the earlier GHRP-6 template and is studied as an agonist of the growth hormone secretagogue receptor (GHS-R1a, the ghrelin receptor). Its literature covers receptor pharmacology, pituitary signaling and animal-model endocrinology. It is a laboratory research compound only. This explainer covers the name, structure, research themes, how it compares with related secretagogues, and what to check on a certificate of analysis. It is coming soon to the V8 catalog as a 10 mg vial: see the GHRP-2 product page.
Where the name GHRP-2 comes from
GHRP-2 stands for growth hormone-releasing peptide 2. The number marks its place in a series of synthetic compounds that grew out of work on met-enkephalin derivatives in the early 1980s, when investigators noticed that certain small peptides could provoke growth hormone release from pituitary cells in culture even though they bore no resemblance to the known hypothalamic releasing hormone. The second member of that series was given the label GHRP-2, and the nonproprietary name pralmorelin is the same molecule. You may also see the developmental code KP-102 in older papers.
The name therefore describes a function seen in assays, not a sequence. To know what the molecule is, you need the structure.
Structure of GHRP-2
GHRP-2 is a hexapeptide with the sequence D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2, where 2-Nal is the unnatural amino acid D-2-naphthylalanine and the C-terminus is amidated. Its molecular weight is about 817.9 g/mol. Three features stand out. First, two of the six residues are D-isomers and one is a bulky naphthyl side chain, which makes the backbone far less recognizable to ordinary peptidases than a chain of natural L-amino acids. Second, the amidated C-terminus removes a free carboxylate. Third, the aromatic residues (naphthylalanine, tryptophan and D-phenylalanine) form a hydrophobic cluster that is central to how the family engages its receptor.
For a refresher on reading one-letter and three-letter notation, see understanding amino acid sequences.
The receptor story: from synthetic peptide to ghrelin
For roughly fifteen years the synthetic secretagogues were compounds in search of a target. In 1996 a receptor was cloned from pituitary and hypothalamic tissue that responded to this class of molecule, and it was named the growth hormone secretagogue receptor, GHS-R. The finding implied that the body must make its own ligand, and the endogenous ligand, the 28-residue acylated peptide ghrelin, was identified soon afterward. The history is covered in the primary literature cited below.
GHS-R1a is a G protein-coupled receptor that signals mainly through the Gq pathway, raising intracellular calcium in responsive cells. GHRP-2 is a full agonist at this receptor in cell-based assays, which is why it is a common reference tool in receptor-binding and signaling work.
What the preclinical literature examines
Everything below is cell-based, animal-model or mechanistic. None of it is a statement about use in people.
Pituitary somatotroph assays. The founding observations were made in cultured rat pituitary cells, where GHRP-family peptides evoke growth hormone release and act together with growth hormone-releasing hormone in a more-than-additive way in many preparations.
Growth hormone-deficient mouse models. Work in little (lit/lit) mice, which carry a defect in the growth hormone-releasing hormone receptor, examined how the pituitary of that animal responds to GHRP-2 and used the response to probe which signaling routes remain intact.
Rat tissue-stress models. A rat burn-injury study used GHRP-2 as a ghrelin-receptor agonist tool and reported changes in the muscle proteolysis-related genes MuRF-1 and MAFbx. These are mechanistic observations in animals, cited here only to show how the compound is used as a probe.
Chemistry and metabolism. Analytical groups have mapped how GHRP-family peptides are broken down in biological samples, and formulation chemists have attached polyethylene glycol to GHRP-2 to examine how modification changes its stability and activity in assays.
Receptor expression and feedback. Rat studies have tracked how GHS-R transcripts in hypothalamic tissue change with growth hormone status, which helps map the feedback loops around the receptor.
A note on interpretation: potency, duration and receptor selectivity differ between preparations and species, so conclusions should be tied to the specific model. Our Hexarelin vs. GHRP-2 comparison and Ipamorelin vs. GHRP-2 comparison show how the primary papers contrast the members of the class.
GHRP-2 and related secretagogues at a glance
These are descriptors only, drawn from the published structures. They are not a ranking.
| Compound | Length | Sequence note | Typical research context |
|---|---|---|---|
| GHRP-2 | 6 residues, about 818 g/mol | D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2 | Pituitary and GHS-R1a signaling, GH-deficient mouse and chronic rodent models |
| GHRP-6 | 6 residues, about 873 g/mol | His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 | Original template for the family; feeding and receptor assays |
| Hexarelin | 6 residues, about 887 g/mol | His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2 | GHS-R1a pharmacology and heart-tissue models |
| Ipamorelin | 5 residues, about 712 g/mol | Aib-His-D-2-Nal-D-Phe-Lys-NH2 | Selective GHS-R1a agonist assays |
| Ghrelin | 28 residues, endogenous | Octanoylated at Ser3 | Natural ligand, reference agonist |
For single-compound background, see what is Hexarelin and what is Ipamorelin.
Why the D-amino acids matter in design
Natural peptides are made of L-amino acids, and most proteases are shaped to cut exactly those. Swapping selected positions to the D-form, as in D-Ala, D-2-Nal and D-Phe here, produces a chain that fits the receptor pocket yet resists many enzymes. The same trick is used across peptide chemistry. For a bench scientist the consequence is practical: a synthesis that accidentally delivers the wrong stereoisomer at one position yields a molecule with the same mass but a different shape, so mass alone cannot prove the product is correct. That is why a sound analytical package pairs chromatography with an identity check, and why lot-to-lot consistency deserves attention.
Questions a lab might ask before ordering
What receptor assay am I running? If the readout is GHS-R1a calcium flux, a well-characterized agonist such as GHRP-2 can serve as a reference, but compare its potency against the control you already use.
Which species? Receptor pharmacology can differ between rat, mouse and cell lines, so match the model to the published work you intend to replicate.
What vial size fits the experiment? The planned catalog format is a 10 mg vial; plan solution preparation with the calculator before opening anything.
Reading the literature critically
Older secretagogue papers often mix several species, routes of exposure and sex-steroid backgrounds, and the compound names are used loosely. When you cite or replicate a study, note the exact peptide, the species, the preparation (cultured cells, tissue, whole animal) and the assay endpoint. Reporting those four details makes results easier to compare across labs.
Handling the lyophilized powder
GHRP-2 is supplied as a freeze-dried powder. General practice for lyophilized peptides applies: keep sealed vials cold, dry and away from light, avoid repeated temperature cycling, and write down the date a vial is first opened. Letting a cold vial reach room temperature before the seal is broken limits condensation on the cake. Tryptophan-containing sequences are sensitive to oxidation over long storage, which is another reason to limit air and light exposure.
Background on the freeze-drying process is in what is lyophilization. For solution-preparation arithmetic, use the peptide calculator rather than a rule of thumb.
What to check on a GHRP-2 certificate of analysis
A hexapeptide containing D-amino acids and a non-natural residue is a good example of why documentation matters: stereochemical errors and truncated sequences can be hard to spot by purity percentage alone.
HPLC purity with the chromatogram, not only a number. Check for minor peaks near the main one and how they are integrated. Understanding HPLC purity explains the figures.
Identity confirmation. As generic buying guidance, ask which method confirms that the molecular weight matches the expected value of about 818 g/mol, and read the report to see the result. The article on purity versus identity testing explains why those are separate questions.
Lot reference and date that match the vial, and the name of the testing laboratory.
Stated fill amount and whether it refers to total powder or net peptide.
V8 Peptides publishes certificates of analysis on the COA page for tested lots. A full walkthrough is in how to read a COA, and the catalog is at the shop.
Common misunderstandings
“GHRP-2 is a form of growth hormone.” It is not. It is a separate small peptide that acts at a receptor; growth hormone is a 191-residue protein.
“GHRP-2 and GHRP-6 are interchangeable.” They share a template but differ in sequence, mass and some assay behavior.
“It works through the same receptor as GHRH analogs.” Releasing-hormone analogs act at a different receptor; GHRP-2 acts at GHS-R1a.
“Regulatory status elsewhere applies here.” Any status in another country does not change that products sold by V8 Peptides are for laboratory research only.
“Animal data predicts human outcomes.” It does not, and this article makes no such claim.
Frequently asked questions
What is GHRP-2?
A synthetic hexapeptide, D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2, from the growth hormone-releasing peptide family, studied as an agonist of the ghrelin receptor GHS-R1a.
Is pralmorelin the same as GHRP-2?
Yes. Pralmorelin is the nonproprietary name for the same molecule. KP-102 is an older developmental code.
What is the molecular weight of GHRP-2?
About 817.9 g/mol.
What does the 2-Nal in the sequence mean?
It is D-2-naphthylalanine, an unnatural aromatic amino acid that makes the chain harder for common peptidases to recognize.
Which receptor does GHRP-2 act on?
The growth hormone secretagogue receptor type 1a, also called the ghrelin receptor, a G protein-coupled receptor.
How is GHRP-2 different from GHRP-6?
They share a template, but GHRP-6 begins with His-D-Trp and has a higher molecular weight of about 873 g/mol, while GHRP-2 uses D-Ala-D-2-Nal.
Is GHRP-2 the same as a growth hormone-releasing hormone analog?
No. Releasing-hormone analogs act on a different receptor. GHRP-2 acts at the secretagogue receptor.
What kind of studies mention GHRP-2?
Pituitary cell assays, receptor signaling work, growth hormone-deficient mouse models and chronic rodent endocrine studies. All preclinical.
What should I look for on a GHRP-2 COA?
An HPLC chromatogram, an identity method confirming the expected mass, a lot reference matching your vial, a test date and a named laboratory.
Is GHRP-2 available from V8 Peptides?
A 10 mg vial is planned for laboratory research use only; check the product page for current status.
References
- Howard AD, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996;273(5277):974-977. PMID: 8688086.
- Bowers CY. History to the discovery of ghrelin. Methods Enzymol. 2012;514:3-32. PMID: 22975043.
- Peroni CN, et al. Growth hormone response to growth hormone-releasing peptide-2 in growth hormone-deficient little mice. Clinics (Sao Paulo). 2012;67(3):265-272. PMID: 22473409.
- Sheriff S, et al. Ghrelin receptor agonist, GHRP-2, attenuates burn injury-induced MuRF-1 and MAFbx expression and muscle proteolysis in rats. Peptides. 2009;30(10):1909-1913. PMID: 19577604.
- Thomas A, et al. Metabolism of growth hormone releasing peptides. Anal Chem. 2012;84(23):10252-10259. PMID: 23101768.
- Hu X, et al. Synthesis of mono-PEGylated growth hormone releasing peptide-2 and investigation of its biological activity. AAPS PharmSciTech. 2015;16(5):1213-1219. PMID: 25761386.
- Bennett PA, et al. Hypothalamic growth hormone secretagogue-receptor (GHS-R) expression is regulated by growth hormone in the rat. Endocrinology. 1997;138(10):4552-4557. PMID: 9348177.
All V8 Peptides products are sold for laboratory research use only. They are not drugs, foods, or cosmetics and are not intended for human or animal consumption.