Description
PrymaLab · Research Use Only
GHRP-2 10mg
Pralmorelin · the only secretagogue with a regulatory approval anywhere
GHRP-2 is the one growth hormone secretagogue that got through a regulatory process. Under the name pralmorelin it was approved in Japan in 2004 as a diagnostic agent for assessing pituitary growth hormone reserve, which no other compound in this class has achieved anywhere.
Specification Table
| Property | Value |
|---|---|
| Compound | GHRP-2 |
| Alternative name | Pralmorelin |
| Class | Growth hormone releasing peptide, hexapeptide |
| Residue count | 6 |
| Molecular weight, calculated | Approximately 818.0 g/mol for the free base |
| CAS | 158861-67-7 |
| Receptor | GHS-R1a, the same receptor ipamorelin acts through |
| Non-coded residue present | A naphthylalanine residue |
| D-configuration residues present | Three, giving substantial protease resistance for a peptide this short |
| Carboxy terminus | Amidated |
| Regulatory status | Approved in Japan in 2004 as a diagnostic agent for growth hormone reserve, marketed by Kaken Pharmaceutical as GHRP Kaken 100 |
| Relationship to that product | Material supplied here is not that product and is not manufactured to pharmaceutical standards |
| Appearance | White lyophilized powder |
| Storage, lyophilized | 2-8°C short term, -20°C for extended storage, protected from light and moisture |
What Does the Japanese Approval Establish?
Pralmorelin holds a diagnostic approval and the word diagnostic is doing real work in that sentence.
A diagnostic agent is approved to produce a measurable response that distinguishes one physiological state from another. It is not approved to change a state.
The basis is that this compound produces a marked rise in circulating growth hormone in individuals with intact pituitary reserve, and a much smaller rise where that reserve is deficient.
The gap between those two responses is the diagnostic signal, and the approval rests on that gap being reliable rather than on the rise itself being useful for anything.
That distinction is routinely lost when the approval is cited on vendor pages, which present it as a general endorsement of the molecule.
What it actually establishes is narrower and more interesting: a regulator examined the response reproducibility closely enough to accept it as a measurement instrument.
For a laboratory that is a meaningful signal, because reproducibility across individuals is exactly the property a research tool needs.
It is also confined to one jurisdiction and one indication, and material supplied here is not that product.
One further point about scope, since it is where most secondary descriptions go wrong.
An approval in one jurisdiction does not travel. Regulators assess separately, and a compound cleared in Japan carries no status in the United States or the European Union by virtue of that clearance.
GHRP-2 has no approval in either. Stating the Japanese approval without stating its boundary reads as broader endorsement than the fact supports.
What Is the Trade Against a Selective Compound?
GHRP-2 and ipamorelin act at the same receptor and behave differently at the pituitary, which is the central comparison in this part of the catalogue.
Both are short synthetic secretagogues binding GHS-R1a. The difference is what else moves when they do.
The published record on GHRP-2 describes measurable increases in adrenocorticotropic hormone, cortisol and prolactin alongside growth hormone, at concentrations that produce the growth hormone response.
Ipamorelin was characterised in 1998 specifically against that background, and the finding was that its growth hormone response occurred where those other outputs did not move appreciably.
Neither profile is better in the abstract. They answer different experimental questions.
A study isolating growth hormone signalling from adrenal and lactotroph effects needs the selective compound, because a confounded readout cannot be deconfounded afterwards.
A study modelling a coordinated pituitary response, or one where the additional outputs are themselves the measurement, has no reason to prefer selectivity and may specifically want the broader profile.
Choosing on potency alone misses this. The two compounds differ in what they do to the preparation, not only in how strongly they do it, and the growth hormone hub sets the full class comparison out.
A methodological note on comparing the two. Published selectivity comparisons were run in defined preparations at defined concentrations, and a profile measured in one system does not automatically hold in another.
The reliable way to use that literature is to check whether the system it used resembles the one being planned, rather than reading the selectivity profile as a fixed property of the molecule.
Where Did This Compound Come From?
GHRP-2 sits in a lineage that started before its receptor was known, which is unusual and worth stating.
Work in the early 1980s identified short synthetic peptides that released growth hormone from pituitary preparations and did not act through the growth hormone releasing hormone receptor.
That was a puzzle. A compound was producing a defined pituitary response through a route nobody could name.
The receptor was not cloned until 1996 and its natural ligand, ghrelin, was not identified until 1999.
So for more than a decade this class existed as a set of synthetic molecules with a known effect and an unknown mechanism, and GHRP-2 was optimised within that period.
That ordering explains the structure. The compound was refined by measuring output rather than by designing against a receptor model, because no receptor model existed.
Three D-configuration residues in six positions is the signature of that approach, arrived at empirically because the substitutions worked.
The result is a molecule that is heavily protease-resistant for its length, which is one reason it survived long enough to reach a regulatory filing.
What Should a GHRP-2 Certificate Show?
Six fields, and the naming question comes first because this compound has several names in circulation.
The full construct written out with configurations at each position. GHRP-2, GHRP-6 and pralmorelin appear on certificates interchangeably and the sequences differ, so a name alone does not specify the article.
Observed mass against calculated mass. At 818 daltons a single deletion is roughly ten to fifteen percent of total mass and any mass spectrometer will resolve it.
Purity by reverse-phase HPLC with the chromatogram supplied, since deletion sequences elute near the main peak and a summary percentage does not show them.
Amidation status of the carboxy terminus, which changes mass and activity and is a routine synthesis failure.
Net peptide content and counterion identity. On an 818 dalton peptide with a basic lysine the trifluoroacetate correction commonly runs near twenty percent.
Lot number and synthesis date.
Because the tryptophan residue absorbs strongly at 280 nanometres, some certificates quantify at that wavelength. That is legitimate and it detects one residue rather than the backbone, so a 214 nanometre trace remains the more informative document.
A note on the naming problem specifically, because it causes more mis-shipments in this class than any analytical failure does.
Numbered names in this family were assigned by the groups that made the compounds rather than by a naming authority, so the numbers carry no structural information.
Two compounds one digit apart can differ at three positions. Reading the sequence rather than the number is the only reliable check.
What Happens Alongside a GHRH Analogue?
This is the one question a catalogue holding both classes should answer, and the published answer is more interesting than a simple additive result.
GHRP-2 acts at GHS-R1a. Sermorelin and tesamorelin act at GHRHR. Two different receptors on the same cell, coupling through overlapping but distinct routes.
When a growth hormone releasing peptide and a GHRH analogue were given together in published human work from 1990, the growth hormone response exceeded the sum of the two given separately.
That is synergy rather than addition, and it is a reproducible finding rather than an isolated report.
The mechanistic account is that the two receptors converge on the somatotroph through different second messenger routes, and that one of them also acts to reduce somatostatin tone, which is the inhibitory input holding the system down.
Removing an inhibition while applying a stimulus produces more than applying the stimulus alone, which is a general principle rather than anything specific to this axis.
For experimental design the consequence is direct. A study combining a secretagogue with a GHRH analogue cannot interpret the result by adding the two single-compound responses together.
It needs its own control arms, and the interaction is the measurement rather than a complication to be subtracted out.
It also means a combination result cannot be attributed to either compound alone, which is a common error in secondary summaries of this literature.
Anyone designing on this axis should read the 1990 work directly rather than a description of it.
How Does It Differ From GHRP-6?
These two are confused more often than any other pair in the catalogue, and the confusion is a labelling problem rather than a chemical one.
Both are hexapeptides. Both are amidated at the carboxy terminus. Both act at GHS-R1a. Both came from the same research programme, and their names differ by one digit.
The sequences differ at three of six positions, which is half the molecule.
GHRP-6 opens with histidine. GHRP-2 opens with a D-alanine and carries a naphthylalanine at position two where GHRP-6 carries a D-tryptophan.
The mass difference is roughly fifty-five daltons, around six percent, which is large enough that any mass spectrometer separates them without difficulty.
So the failure is never analytical. A laboratory that runs a mass check catches a substitution immediately, and the vast majority of mis-shipments in this pair are caught by nobody because nobody runs the check.
The two also differ in published profile. GHRP-6 is associated with a more pronounced effect on appetite signalling than GHRP-2, which follows from where each sits relative to the natural ligand rather than from potency.
A study that ordered one and received the other would produce internally consistent data pointing at the wrong compound.
The defence is to read the sequence on the certificate rather than the name on the vial, and to record the observed mass rather than accepting the stated one.
That is two minutes of work and it is the only check that distinguishes these two before the experiment rather than after it.
How Should the Vial Be Handled?
Storage matches the rest of the short secretagogues, with one residue-specific caution.
Lyophilized powder is stable sealed against moisture at 2 to 8 degrees Celsius short term and at minus 20 for longer, protected from light.
The light requirement is not boilerplate here. Tryptophan is photosensitive and oxidises on exposure, which changes mass by sixteen daltons per oxygen added and is detectable if anyone looks.
Amber vials or foil overwrap are the standard answer and both are cheap relative to the material.
Bring the vial to room temperature before opening, since the powder is hygroscopic and cold glass condenses moisture immediately.
Reconstitute by adding diluent down the wall and swirling rather than shaking, and aliquot on first reconstitution rather than freeze-thawing the whole volume repeatedly.
Use low-binding consumables at working dilutions. Adsorption removes a measurable fraction of any dilute peptide from small-volume plastics.
Record lot, net peptide content, diluent volume and date of first reconstitution, which is the minimum another laboratory needs to reproduce the preparation.
Published Literature
Selected references on the origin of this class, on the receptor, and on the approved diagnostic formulation.
- Bowers CY, Momany FA, Reynolds GA, Hong A. Endocrinology. 1984;114(5):1537-1545. DOI: 10.1210/endo-114-5-1537
- Bowers CY, Reynolds GA, Durham D, Barrera CM, Pezzoli SS, Thorner MO. Journal of Clinical Endocrinology and Metabolism. 1990;70(4):975-982. DOI: 10.1210/jcem-70-4-975
- Drugs in R&D. 2004;5(4):236-239. PMID: 15230633
- 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
Frequently Asked Questions
What is GHRP-2?
A six-residue synthetic growth hormone releasing peptide acting at GHS-R1a, calculated at approximately 818 daltons for the free base, also known as pralmorelin.
Does it hold a regulatory approval?
Yes. It was approved in Japan in 2004 as a diagnostic agent for assessing pituitary growth hormone reserve, marketed by Kaken Pharmaceutical as GHRP Kaken 100. No other compound in this class holds an approval anywhere.
What does a diagnostic approval mean?
That the compound is approved to produce a measurable response distinguishing one physiological state from another. It is not approved to change a state, which is a different regulatory category.
What is the diagnostic signal?
The gap between responses. Circulating growth hormone rises markedly where pituitary reserve is intact and much less where it is deficient, and the approval rests on that gap being reliable.
Does that approval apply to this material?
No. Material supplied here is research-grade peptide under research-use-only terms, is not manufactured to pharmaceutical standards, and is not the approved product.
How does it differ from ipamorelin?
Both act at GHS-R1a. The published record on GHRP-2 describes measurable increases in adrenocorticotropic hormone, cortisol and prolactin alongside growth hormone, at concentrations producing the growth hormone response.
Which is the better compound?
Neither in the abstract. A study isolating growth hormone signalling needs the selective compound because a confounded readout cannot be deconfounded afterwards. A study modelling a coordinated pituitary response has no reason to prefer selectivity.
Why is this class older than its receptor?
Because the compounds were found first. Short peptides releasing growth hormone through a non-GHRH route were identified in the early 1980s, the receptor was cloned in 1996, and its natural ligand ghrelin was identified in 1999.
How did that affect the structure?
It was optimised by measuring output rather than by designing against a receptor model, since no model existed. Three D-configuration residues in six positions is the signature of that empirical approach.
What makes the naming question important on a certificate?
GHRP-2, GHRP-6 and pralmorelin appear on certificates interchangeably and the sequences differ. A name alone does not specify the article, so the full construct with configurations should be written out.
Why does light protection matter here specifically?
The tryptophan residue is photosensitive and oxidises on exposure, adding sixteen daltons per oxygen. Amber vials or foil overwrap are the standard answer and both are cheap relative to the material.
What detection wavelength should be used?
The certificate should state which. Tryptophan absorbs strongly at 280 nanometres so quantification there is legitimate, and a 214 nanometre trace remains more informative because it detects the backbone rather than one residue.
Compliance Statement
GHRP-2 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, pralmorelin holds a diagnostic approval in Japan for assessing pituitary growth hormone reserve but that approval attaches to a specific pharmaceutical product in one jurisdiction and material supplied here is not that product, 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-2
GHRP-2 is also stocked as GHRP-2 Nasal Spray, GHRP-2 10mg preloaded 3ml pen and GHRP-2 5mg. Each listing states its own quantity and concentration, and the pen and vial comparison explains what changes between formats.
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