Description
PrymaLab · Research Use Only
GHRP-6 10mg
The closest of the family to the natural ligand
GHRP-6 is the member of its family that behaves most like ghrelin, the natural ligand of the receptor they all bind. That overlap is the most useful thing to know about it, because it decides which experiments the compound suits and which ones it quietly confounds.
Specification Table
| Property | Value |
|---|---|
| Compound | GHRP-6 |
| Class | Growth hormone releasing peptide, hexapeptide |
| Residue count | 6 |
| Molecular weight, calculated | Approximately 873.0 g/mol for the free base |
| CAS | 87616-84-0 |
| Receptor | GHS-R1a |
| Aromatic residues | Two tryptophans, which is unusual for a peptide this short and governs storage |
| D-configuration residues present | Two |
| Carboxy terminus | Amidated |
| Relationship to hexarelin | Hexarelin is this sequence carrying one added methyl group on the position 2 residue |
| Salt form | Acetate as supplied. Confirm against the certificate |
| Regulatory status | No approved human or veterinary formulation in any jurisdiction |
| Appearance | White lyophilized powder |
| Purity | Per lot-specific certificate of analysis |
| Storage, lyophilized | 2-8°C short term, -20°C for extended storage, protected from light and moisture |
What Separates GHRP-6 From the Rest of the Family?
All of these compounds bind the same receptor, so the differences between them are differences of degree rather than of target, and one of those differences is larger than the others.
GHS-R1a has a natural ligand, ghrelin, identified in 1999 and produced mainly in the stomach.
Ghrelin does two things through that receptor. It drives growth hormone release from the pituitary and it drives appetite signalling through hypothalamic circuits.
The synthetic compounds in this family reproduce the first effect, and they differ in how much of the second they carry with it.
GHRP-6 carries more of it than any other member. The published record consistently reports a stronger orexigenic signal for this compound than for the selective secretagogues, and that is the single most useful discriminator when choosing between them.
That is a property of the experiment rather than of the molecule.
A study modelling ghrelin biology wants the compound that behaves most like ghrelin, and this is it. A study isolating the somatotroph response does not, because feeding behaviour is now a variable in the system.
Choosing GHRP-6 for a growth hormone study and then observing an unexplained change in intake is the predictable version of that mistake.
Why Do Two Tryptophans Change the Handling?
Six residues and two of them tryptophan is an unusual composition, and it sets the storage requirement for this compound more than anything else on the certificate.
Tryptophan is the most photosensitive of the twenty standard residues. Light exposure drives oxidation of the indole ring, and the products include N-formylkynurenine and kynurenine.
Each oxidation event adds oxygen. Mass moves by sixteen daltons, or thirty-two where both rings have gone.
On an 873 dalton molecule that is roughly two to four percent, which is detectable on any instrument if anyone thinks to look.
Two tryptophans means two independent sites. What accumulates is a mixture rather than one species.
That is why light exclusion on this compound is a requirement rather than a habit. Amber glass or a foil overwrap costs almost nothing against the value of the material.
The same chemistry gives a useful analytical handle. Tryptophan absorbs strongly at 280 nanometres, so ultraviolet quantification is straightforward here in a way it is not for a peptide with no aromatic residue.
A 214 nanometre chromatogram remains the more informative document, because it reads the backbone rather than two side chains, and the oxidised species separate cleanly on a reverse-phase gradient regardless of wavelength.
Where Does This Compound Sit Historically?
GHRP-6 is the original member of the family and the compound the whole class was built from, which is worth knowing when reading the literature.
Work in the early 1980s identified short synthetic peptides that released growth hormone from pituitary preparations through a route that was not the growth hormone releasing hormone receptor.
GHRP-6 came out of that programme and became the reference compound for everything that followed.
That has a practical consequence for anyone reading the older papers. A great deal of the foundational pharmacology of this receptor was characterised using GHRP-6 before the receptor itself had been cloned in 1996 or its natural ligand identified in 1999.
So the compound functions as a historical control. A result obtained with a newer analogue can be compared against a GHRP-6 result from a paper written when nobody knew what the target was.
Every later compound in the family was developed by modifying this scaffold. Hexarelin adds a methyl group to the position 2 residue, and GHRP-2 replaces two positions outright.
Reading the family as a set of edits to one starting sequence makes the structure-activity literature considerably easier to follow than treating each as a separate molecule.
The growth hormone hub sets out how the wider class divides, including the compounds acting on the other receptor entirely.
What Should a GHRP-6 Certificate Show?
Seven fields, and the first two exist because of the naming problem this family has.
The full construct written out with configurations at each position. Numbered names in this family were assigned by the groups that made the compounds rather than by any naming authority, so the number carries no structural information.
Observed mass against calculated mass. At 873 daltons a deletion is over ten percent of total mass and any instrument resolves it, so this single figure closes most of the identity risk.
Purity by reverse-phase HPLC with the chromatogram supplied rather than a summary percentage, since oxidised tryptophan species and deletion sequences both elute close to the main peak.
Whether the carboxy terminus is amidated. The free acid weighs one dalton more, behaves differently at the receptor, and is a routine synthesis failure.
Counterion identity and net peptide content. This is supplied as an acetate, which is not the default outcome of reverse-phase purification, so the exchange step should be documented rather than assumed.
Lot number and synthesis date, tying every other figure to the vial that ships.
Whether the material was protected from light through packing and shipping, which few certificates state and which matters more here than for almost anything else in the catalogue.
One further note on the acetate question, since this compound is supplied in that form rather than the usual one.
Reverse-phase purification with trifluoroacetic acid leaves trifluoroacetate paired to every basic site. Getting to an acetate requires a separate ion-exchange step.
That step is real work and it is not free, so a supplier claiming an acetate form without documenting the exchange is claiming something they may not have done.
Residual trifluoroacetate is measurable by ion chromatography or by fluorine nuclear magnetic resonance, and a figure from either settles it.
What Should the Study Measure?
Growth hormone is not secreted at a steady rate, and that single fact decides whether a secretagogue experiment produces an interpretable number or a meaningless one.
Release is pulsatile. Concentration in a sampled compartment rises and falls on a timescale of tens of minutes, driven by the interaction of releasing and inhibiting inputs.
A single measurement taken at one moment therefore samples a moving quantity.
Two identical preparations sampled twenty minutes apart can return figures differing by an order of magnitude, and neither reading is wrong.
The endpoint that survives this is area under the curve across a defined window, which requires serial sampling rather than a single draw.
Peak concentration is the second usable endpoint and it needs a sampling interval short enough to catch the peak rather than its shoulder.
How short depends on the preparation. In cell culture the response is faster and the window narrower than in a whole animal, so an interval that works in one system misses the peak in the other.
Baseline matters as much as the response. Secretion continues without any added compound, so a pre-sample establishes what the system was doing before the experiment started.
Omitting that pre-sample is the most common design fault in this area and it cannot be corrected afterwards.
None of this is specific to GHRP-6. It applies to every compound in this class, and it is worth settling before any of them is ordered.
How Should the Vial Be Handled?
Dry storage is straightforward and the light requirement is the part that gets skipped.
Sealed lyophilized powder holds at 2 to 8 degrees Celsius for short periods and at minus 20 for longer, with light excluded at every stage including the bench.
Bring the vial to ambient temperature before breaking the seal, since the powder is hygroscopic and cold glass pulls atmospheric moisture straight onto the cake.
Reconstitute by running diluent down the vial wall and swirling rather than shaking. Agitation at the air-liquid interface is the main aggregation route for any peptide and costs nothing to avoid.
Aliquot on first reconstitution. Repeated freeze-thaw of a whole volume is the most avoidable loss in peptide work and it cannot be reversed.
Keep working dilutions out of the light as well. Photo-oxidation acts on the molecule in solution more readily than on the dry solid, so a tube left on an illuminated bench is the realistic failure case.
Use low-binding consumables at low working concentrations, since adsorption removes a measurable fraction of dilute peptide into ordinary polypropylene.
Record lot, net peptide content, diluent volume and date of first reconstitution. Those four fields are what another laboratory needs to reproduce the preparation.
One last point on documentation rather than on chemistry.
Where a vial has been opened more than once, the number of openings belongs in the record alongside the date.
Each opening exposes the remaining powder to atmospheric moisture, and a vial opened five times is not the same material as one opened once, even where both were resealed carefully.
That figure costs nothing to record and it explains discrepancies that otherwise look like assay drift.
Published Literature
Selected references on the origin of this class, on the receptor and on its natural ligand.
- Bowers CY, Momany FA, Reynolds GA, Hong A. Endocrinology. 1984;114(5):1537-1545. DOI: 10.1210/endo-114-5-1537
- Howard AD, Feighner SD, Cully DF, Arena JP, Liberator PA, Rosenblum CI, et al. Science. 1996;273(5277):974-977. DOI: 10.1126/science.273.5277.974
- Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H, Kangawa K. Nature. 1999;402(6762):656-660. DOI: 10.1038/45230
- Wren AM, Small CJ, Ward HL, Murphy KG, Dakin CL, Taheri S, et al. Endocrinology. 2000;141(11):4325-4328. DOI: 10.1210/endo.141.11.7873
- Bowers CY. Cellular and Molecular Life Sciences. 1998;54(12):1316-1329. DOI: 10.1007/s000180050257
Frequently Asked Questions
What is GHRP-6?
A six-residue synthetic growth hormone releasing peptide acting at GHS-R1a, calculated at approximately 873 daltons for the free base, and the original member of the GHRP family.
What separates it from the other GHRPs?
How much appetite signalling it carries alongside the growth hormone response. The published record reports a stronger orexigenic signal for GHRP-6 than for the selective secretagogues.
Why does that happen?
Because the receptor they all bind has a natural ligand, ghrelin, which drives both growth hormone release and hypothalamic appetite circuits. GHRP-6 reproduces more of the second effect than the others do.
Is that a problem?
Only relative to the experiment. A study modelling ghrelin biology wants the compound that behaves most like ghrelin. A study isolating the somatotroph response has just added feeding behaviour as a variable.
Why do the two tryptophans matter?
Tryptophan is the most photosensitive standard residue. Light drives oxidation of the indole ring, adding sixteen daltons per oxygen, and two tryptophans means two independent sites and a mixture rather than one species.
How large is that mass change?
Roughly two to four percent on an 873 dalton molecule depending on the extent of oxidation, which any mass spectrometer detects if anyone thinks to look for it.
Does that help analytically?
Yes. Tryptophan absorbs strongly at 280 nanometres, so ultraviolet quantification is straightforward here in a way it is not for a peptide carrying no aromatic residue.
Which wavelength should the certificate use?
It should state which. A 214 nanometre trace remains more informative because it reads the peptide backbone rather than two side chains, and oxidised species separate cleanly at either wavelength.
How does it relate to hexarelin?
Hexarelin is this sequence carrying one added methyl group on the position 2 residue. The later compounds in this family were all developed by modifying the GHRP-6 scaffold.
Why is the acetate form worth checking?
Because acetate is not the default outcome of reverse-phase purification. Trifluoroacetate is. An acetate form means an ion-exchange step was performed, and that step should be documented rather than assumed.
What makes the naming question important?
Numbers in this family were assigned by the groups that made the compounds rather than by a naming authority, so they carry no structural information. Reading the sequence is the only reliable check.
How should the vial be stored?
Sealed and dry at 2 to 8 degrees Celsius short term or minus 20 for longer, with light excluded at every stage including the bench and any working dilutions.
Compliance Statement
GHRP-6 is sold exclusively for laboratory research use. It is not a drug, food, or cosmetic product, and it is not a dietary product of any kind. It is not approved by the FDA or any comparable authority for human or veterinary use, published reports of appetite signalling describe measurements made in defined experimental systems rather than properties that transfer to any other setting, and no compound in this range is offered for any human or veterinary purpose. This product is not intended to diagnose, treat, cure, or prevent any disease. It must not be given to humans or animals. Purchase is restricted to qualified researchers and institutions operating within applicable laws. All handling is the responsibility of the purchasing laboratory.
Other formats of GHRP-6
GHRP-6 is also stocked as GHRP-6 10mg Nasal Spray, GHRP-6 10mg preloaded 3ml pen and GHRP-6 5mg. Each listing states its own quantity and concentration, and the pen and vial comparison explains what changes between formats.
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