Quick answer: Hexarelin (about 887 Da) and GHRP-2 (about 818 Da) are both six-residue ghrelin-receptor peptides that share only their last four positions. A purity percentage cannot tell them apart; a measured mass on the certificate can.
Two hexapeptides that are often grouped together
Hexarelin and GHRP-2 are both six-residue synthetic peptides from the growth hormone-releasing peptide family. Both act at the ghrelin receptor, both appear in the same catalog sections, and both turn up in the same forum threads. Despite that, they are two different molecules with different sequences and different masses, and a vial labeled with one name should never be assumed to behave like the other in an assay.
This guide compares them on origin, structure, receptor background, what the published literature reports and what a certificate should show. It is background for laboratory research use only. Nothing here describes an effect or a use in people or animals. Single-compound background is in the hexarelin research overview and the what is hexarelin explainer.
Origin: one family, two different modifications
The family began in the early 1980s, when Cyril Bowers and colleagues described synthetic peptides that released growth hormone from pituitary cells. GHRP-6 was the first widely cited member. Later work in the same tradition produced analogs that swapped residues to change potency and stability in the models of the day, and both hexarelin and GHRP-2 belong to that second wave.
Hexarelin kept the GHRP-6 layout and changed a single residue, replacing D-tryptophan with D-2-methyltryptophan. GHRP-2 took a larger step: it replaced the N-terminal histidine with D-alanine and introduced D-2-naphthylalanine, a bulky non-natural residue. The result is that hexarelin reads as a close edit of GHRP-6, while GHRP-2 reads as a more heavily redesigned relative.
All of these peptides were characterized before their receptor was known. The receptor was cloned in 1996 and its natural ligand, ghrelin, was identified in 1999, which retroactively explained why the whole family behaved as it did. A short companion piece on the older sibling is the hexarelin vs. GHRP-6 comparison.
Side-by-side comparison
| Feature | Hexarelin | GHRP-2 |
|---|---|---|
| Family | Growth hormone-releasing peptide (hexapeptide) | Growth hormone-releasing peptide (hexapeptide) |
| Sequence | His-D-2-Me-Trp-Ala-Trp-D-Phe-Lys-NH2 | D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2 |
| Shared positions | Ala, Trp, D-Phe, Lys (positions 3 to 6) | Ala, Trp, D-Phe, Lys (positions 3 to 6) |
| Approximate mass | About 887 Da | About 818 Da |
| Main receptor | Ghrelin receptor (GHS-R1a) | Ghrelin receptor (GHS-R1a) |
| Other binding reported | CD36 (cardiac tissue models) | Not a feature of its literature |
| Key identity check | Measured mass near 887 Da | Measured mass near 818 Da |
| Listed by V8 | Yes, research use only | No |
Structure: how much of the sequence is shared
Hexarelin is His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2. GHRP-2 is D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2. Reading the two side by side, the last four positions are the same: Ala, Trp, D-Phe and Lys, with an amidated C-terminus on both. The first two positions differ. Hexarelin starts with a histidine and a methylated D-tryptophan; GHRP-2 starts with D-alanine and a D-naphthylalanine.
That difference shows up in the mass. Hexarelin is about 887 Da and GHRP-2 is about 818 Da, a gap of roughly 69 Da. The gap is large enough that a mass spectrometer separates them cleanly, but a purity percentage from HPLC does not. Both are hexapeptides built mostly from hydrophobic aromatic residues, and each can produce one sharp peak on a standard gradient.
Both are supplied as lyophilized powders. Neither carries a metal, a lipid chain or a linker, so their chemistry is simpler than that of larger analogs. The D-residues, however, are a reminder that these sequences depend on correct stereochemistry at several positions, which matters when you read a certificate.
Receptor background
Both peptides are agonists at the growth hormone secretagogue receptor type 1a, the receptor that also binds ghrelin. Howard and colleagues reported its cloning in 1996, and Kojima and colleagues identified ghrelin as the natural ligand three years later. In receptor terms, the two compounds sit in the same pharmacological class.
Hexarelin has one extra thread in its literature. Work by Bodart and colleagues reported that hexarelin also binds CD36, a scavenger receptor expressed on several cell types, and proposed a role for that interaction in cardiac tissue models. That finding belongs to the hexarelin literature specifically and should not be transferred to GHRP-2 without a citation. In the other direction, GHRP-2 has its own reports in animal and cell systems that should be read in their own context rather than blended with hexarelin results.
The practical point for a bench scientist is that shared receptor class does not mean shared data. A methods section should name the exact peptide, because results for one cannot be read as results for the other.
What the published work reports
Most older work on both compounds is receptor pharmacology in cell lines and animal models, along with reports on how responses change over repeated exposure in experimental systems. Several papers on hexarelin describe a fading response under repeated exposure, and reviews of the family discuss similar patterns across the group. Review articles such as Smith and colleagues (1997) are the best starting point for the family as a whole.
Because the two peptides were studied by different groups under different conditions, direct head-to-head numbers are scarce. Be cautious with any summary table that lines up potency figures from separate papers. Differences in assay, species, preparation and purity can account for more of the gap than the molecules themselves.
What a certificate should show
For two peptides this close in family, the identity check carries most of the weight. Look for a measured mass next to the expected value, the exact compound name, and a lot identifier and test date that match the vial. For background on reading these documents, see understanding HPLC purity and how to read a COA.
A chromatogram is worth reading as well as the percentage. Solid-phase synthesis of a hexapeptide with several D-residues can leave small populations of deletion or racemized sequences, and these may sit close to the main peak. For cell work, look for an endotoxin result and a sterility statement.
V8 Peptides publishes certificates for only some products. Where one exists, it reports HPLC purity and identity, endotoxin and PCR sterility. This article describes general buyer practice and is not a statement about any particular lot. V8 lists hexarelin at hexarelin and does not list GHRP-2. More buyer-side guidance is in where to buy hexarelin and choosing a peptide supplier.
Handling and record keeping
Keep lyophilized peptide cold, dry and away from light until use, and write the opening date on the vial. Plan aliquots before opening so a vial is not handled repeatedly. This guide gives no volumes or concentrations, because those belong in a laboratory's own validated procedure.
In the notebook, record the exact name, lot, supplier, certificate date, storage conditions and opening date. When two related secretagogues share a study, label them as separate reagents with separate controls from the first day, so a later reader can tell which one produced a result.
Frequently asked questions
Are hexarelin and GHRP-2 the same peptide?
No. They are both six-residue peptides, but they share only the last four positions. The first two differ, and the masses differ by roughly 69 Da.
How different are they in mass?
About 887 Da for hexarelin against about 818 Da for GHRP-2.
Which receptor do they act on?
Both act at the growth hormone secretagogue receptor type 1a, the receptor that also binds ghrelin.
Can HPLC purity tell them apart?
Not on its own. Both are aromatic hexapeptides and can each show a single clean peak. A measured mass next to the expected mass is the identity check.
What is D-2-Nal?
D-2-naphthylalanine, a bulky non-natural amino acid found at position 2 of GHRP-2.
Why does CD36 come up for hexarelin?
Published work reported that hexarelin binds CD36 as well as the ghrelin receptor. That finding belongs to the hexarelin literature specifically.
Which one is closer to GHRP-6?
Hexarelin. It differs from GHRP-6 by one methyl group, while GHRP-2 has a more heavily modified N-terminus.
Does V8 sell GHRP-2?
No. V8 lists hexarelin, for laboratory research use only.
Why read the chromatogram and not just the percentage?
With several D-residues, stereochemical impurities can sit close to the main peak and be hidden inside one headline number.
Does this article describe a use in people?
No. It summarizes structure, published background and analytical practice. No product is sold for human or animal consumption.
What should I record for each vial?
The exact compound name, lot identifier, certificate date, supplier, storage conditions and the date the vial was opened.
References
- 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;114(5):1537-1545.
- Howard AD, Feighner SD, Cully DF, et al. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996;273(5277):974-977.
- Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H, Kangawa K. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999;402(6762):656-660.
- Bodart V, Febbraio M, Demers A, et al. CD36 mediates the cardiovascular action of growth hormone-releasing peptides in the heart. Circ Res. 2002;90(8):844-849.
- Smith RG, Van der Ploeg LH, Howard AD, et al. Peptidomimetic regulation of growth hormone secretion. Endocr Rev. 1997;18(5):621-645.