Hexarelin is a synthetic six-residue growth hormone releasing peptide (GHRP) with the sequence His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2, developed as a metabolically stabilised analogue of GHRP-6 and studied both as a growth hormone secretagogue receptor (GHS-R1a) agonist and as a ligand for the cardiac scavenger receptor CD36. That dual-target profile is what makes hexarelin distinctive in the secretagogue literature: a substantial part of its published record concerns cardiovascular models in which growth hormone release does not account for the observations reported.
MyPeptide supplies Hexarelin as a lyophilized powder in 2 mg and 5 mg sealed vials, part of the GHRPs and secretagogues range. It is offered strictly as a research chemical for in-vitro and preclinical laboratory work, not for human or veterinary use.
What is Hexarelin?
Hexarelin is a synthetic hexapeptide, also catalogued as examorelin and EP-23905. It belongs to the GHRP family — short peptides that stimulate pituitary somatotrophs through the ghrelin receptor (GHS-R1a) rather than through the GHRH receptor. Chemically it is a small, fully synthetic molecule: molecular formula C47H58N12O6, molecular weight 887.04 g/mol, CAS number 140703-51-1, terminating in a C-terminal amide.
In laboratory use hexarelin functions as a reference agonist. Where a study needs a well-characterised, high-efficacy GHS-R1a ligand against which to benchmark a newer secretagogue, hexarelin is one of the compounds the literature reaches for, alongside GHRP-2 and ipamorelin.
Origin and structure
The GHRP series originated with the enkephalin-derived work of Cyril Bowers in the 1970s and 1980s, which produced GHRP-6. Hexarelin was developed from that scaffold by Romano Deghenghi and colleagues in the early 1990s. The two peptides differ by a single methyl group: the D-tryptophan at position 2 of GHRP-6 is replaced by 2-methyl-D-tryptophan in hexarelin.
That substitution is a classic peptide-stabilisation move. Adding steric bulk adjacent to the indole ring has been reported to slow enzymatic clearance and to raise potency at the receptor, and the D-amino acids at positions 2 and 5 already protect the backbone against the aminopeptidases that would rapidly clear an all-L hexapeptide. The C-terminal amide removes the free carboxylate, a further stability feature shared across the GHRP family.
Structurally, hexarelin bears no resemblance to growth hormone itself and no meaningful homology to GHRH. It is a peptidomimetic of ghrelin's active core rather than a fragment of any human hormone, which is why the GHRP class is described as a synthetic secretagogue family rather than as analogues.
How Hexarelin is thought to work
The primary mechanism reported for hexarelin is agonism at GHS-R1a, a G-protein-coupled receptor expressed on pituitary somatotrophs and in the hypothalamic arcuate nucleus. Receptor occupancy is coupled to Gq/phospholipase C signalling, inositol trisphosphate generation and a rise in intracellular calcium, which in pituitary preparations is associated with secretory granule release. Published work also describes a permissive interaction with endogenous GHRH tone and partial functional antagonism of somatostatin, so the amplitude of the response observed in intact animals depends on the hypothalamic state at the time of administration, not on the peptide alone.
The second, and more unusual, arm of the mechanism is CD36. Hexarelin binding to this scavenger receptor was reported in cardiac membrane preparations, and CD36 is expressed in cardiomyocytes, macrophages and endothelium. Because CD36 is not a growth hormone pathway, effects reported in cardiac models — including those in hypophysectomised or GH-deficient animals — are generally attributed to this route rather than to the somatotropic axis. Investigators use hexarelin partly as a pharmacological probe to separate the two.
A third mechanistic feature reported consistently across the GHRP literature is receptor desensitisation. Continuous or closely repeated exposure attenuates the secretory response in a way that pulsatile exposure does not, a property attributed to GHS-R1a internalisation. Any experimental design using hexarelin over more than a single time point has to account for this.
What the research has examined
Growth hormone and the IGF-1 axis
Rodent and cell-based pituitary work from the 1990s onward reported hexarelin to be among the more potent secretagogues of its generation, producing larger amplitude GH release than GHRP-6 in matched comparisons. Human pharmacology studies were conducted during its clinical development and reported GH release after intravenous, subcutaneous, intranasal and oral administration, with progressively lower bioavailability across those routes. Development did not proceed to approval, and no marketed product exists. Downstream IGF-1 responses were measured in some of that work as a secondary readout.
Cardiac and vascular models
The cardiovascular literature is the reason hexarelin remains in circulation as a research tool. Rodent studies in ischaemia–reperfusion and post-infarction models reported changes in cardiac contractile parameters and in markers of cardiomyocyte survival, and comparable observations in GH-deficient animals argued for a GH-independent route. Binding studies subsequently identified CD36 as the relevant target. This body of work is preclinical; the endpoints are haemodynamic and histological measurements in animals, not clinical outcomes.
Selectivity and off-target hormone release
Unlike ipamorelin, hexarelin is not a selective secretagogue. Published human and animal work reported concurrent elevations in cortisol, ACTH and prolactin, an important consideration when a study design needs a clean GH signal. This contrast is the practical basis for choosing between the two compounds and is examined in detail in our hexarelin vs ipamorelin comparison.
Skeletal muscle and metabolic models
Smaller preclinical literatures have examined hexarelin in muscle-wasting and cachexia models and in adipose tissue preparations, generally as one arm within a broader look at ghrelin-receptor pharmacology. These are exploratory animal and cell-culture findings rather than an established research consensus.
Forms and sizes we supply
| Attribute | Specification |
|---|---|
| Product | Hexarelin (examorelin, EP-23905) |
| Form | Lyophilized powder, sealed glass vial |
| Available sizes | 2 mg, 5 mg |
| Purity | ≥99% by HPLC, lot-matched COA available |
| CAS number | 140703-51-1 |
| Molecular formula | C47H58N12O6 |
| Molecular weight | 887.04 g/mol |
| Sequence | His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2 |
| Primary target | GHS-R1a (ghrelin receptor) |
| Secondary target | CD36 scavenger receptor |
| Intended use | Laboratory research only |
The 2 mg vial suits short in-vitro series and receptor assays; the 5 mg vial is the more economical unit where a laboratory is running repeated preparations from a single lot and wants to avoid lot-to-lot variation mid-study. Ordering considerations are covered separately in our hexarelin buying guide.
Reconstitution and storage in a lab context
Hexarelin ships as a lyophilized cake and is reconstituted with bacteriostatic water for multi-draw work or sterile water where a preservative would interfere with the assay. Solvent is directed down the vial wall rather than onto the cake, and the vial is swirled rather than shaken; the small hexapeptide dissolves readily, and vigorous agitation mainly produces foam that complicates accurate withdrawal.
The concentration arithmetic is a straightforward laboratory calculation. A 5 mg vial made up with 2 mL of diluent yields 2.5 mg/mL, or 2,500 mcg/mL; 0.1 mL drawn on a U-100 syringe (the 10-unit mark) contains 250 mcg of peptide. The same 5 mg vial made up with 5 mL yields 1 mg/mL and 100 mcg per 0.1 mL. The full method is set out in our reconstitution guide, with the arithmetic in reconstitution math explained.
Sealed lyophilized vials are held at −20 °C, protected from light and moisture. Reconstituted material is kept at 2–8 °C and used within the study window; where a series will run over weeks, aliquoting into sterile empty vials and freezing avoids repeated freezing and thawing of a single stock. General practice is summarised in how to store peptides.
Purity, COA and how to read it
Every hexarelin lot is supplied with a certificate of analysis matched to the lot number on the vial. The two entries that carry the most weight are the HPLC chromatogram, which reports purity as the main peak's share of total peak area, and the mass spectrometry result, which confirms identity against the expected 887.04 g/mol. Purity above 99% and an observed mass matching the theoretical value within instrument tolerance together indicate that the vial contains the intended molecule and little else.
Two details specific to this compound are worth checking. First, the mass spectrum should be consistent with the 2-methyl-tryptophan analogue rather than with GHRP-6, since the pair differ by only 14 Da — a difference a careless reading could miss. Second, the counter-ion should be stated: peptides purified by reversed-phase chromatography usually arrive as a TFA salt, and salt content affects the net peptide mass in the vial. Our guide to reading a peptide COA walks through a full certificate line by line.
Regulatory status
Hexarelin has no marketing authorisation in the United States or elsewhere. Clinical development in the 1990s did not result in an approved product, so there is no reference-listed medicine and no approved labelling. Material supplied here is a research-use-only chemical intended for laboratory investigation by qualified personnel. It is not a supplement, not a medicine, and is not supplied for human or veterinary administration. Hexarelin is also listed as a prohibited substance in sport under anti-doping rules covering growth hormone secretagogues.
Related peptides and further reading
Within the same receptor family, ipamorelin is the selective counterpart, GHRP-2 the potency-focused one and GHRP-6 the parent scaffold hexarelin was built from. Researchers pairing a secretagogue with a GHRH-side compound generally look to the GHRH analogue range. Broader context on how these classes fit together is in our muscle growth research overview and the pituitary and hypothalamus research hub.