Hexarelin is a synthetic six-amino-acid peptide with the sequence His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2. It also goes by examorelin and the development codes EP-23905 and MF-6003. The compound was developed by the Italian firm Mediolanum Farmaceutici, and according to its Wikipedia entry it reached Phase II clinical trials for growth hormone deficiency and congestive heart failure but did not finish development and was never brought to market.
It belongs to the family of growth hormone secretagogues, specifically the growth hormone-releasing peptides (GHRPs). These peptides share no sequence similarity with ghrelin, the body's natural hunger and GH-release hormone, but they act on the same target.
How it works
Hexarelin is an agonist at the growth hormone secretagogue receptor (GHS-R1a), the same G-protein-coupled receptor that ghrelin binds. The receptor sits on the somatotroph cells of the anterior pituitary and in several brain regions. When hexarelin activates it, downstream phospholipase C signaling raises intracellular calcium and triggers GH release. That pathway is separate from, and can be additive to, the cAMP-dependent route used by growth hormone-releasing hormone (GHRH).
The GH effect is not the whole story. Human and animal work shows hexarelin also raises prolactin, ACTH, and cortisol, so it engages the hypothalamic-pituitary-adrenal axis as well, an effect researchers have linked to arginine vasopressin (J Clin Endocrinol Metab, 1999).
What the research actually shows
Unlike most peptides in this category, hexarelin was tested in people. In one study, seven male volunteers received intravenous hexarelin or recombinant GH. Hexarelin produced a short-lived positive inotropic effect, with left ventricular ejection fraction rising from about 64% to 71% (p<0.03), peaking at 30 minutes and lasting up to an hour, while blood pressure and heart rate stayed flat. The authors noted this cardiac effect appeared independent of the GH rise and may run through GH-secretagogue receptors in the heart itself (J Endocrinol Invest, 1999). Related work looked at hexarelin in growth hormone-deficient adults and in dilated cardiomyopathy patients (PubMed, 2001).
One practical finding from the human data: the GH-releasing effect fades with repeated dosing. Wikipedia, citing the clinical literature, notes a partial and reversible tolerance, on the order of a 50–75% drop in efficacy over weeks to months of continued use.
Despite the Phase II program in GH deficiency and heart failure, the compound was discontinued and never approved by any regulator. Most of the cardioprotective mechanism work that followed has been in rats and mice, not humans.
Anti-doping status
Growth hormone secretagogues, including GHRPs like hexarelin, are banned by the World Anti-Doping Agency under category S2 (peptide hormones, growth factors, related substances, and mimetics), and the prohibition applies at all times, in and out of competition. Athletes subject to testing can face sanctions for it.
For buyers: research-use-only and quality
Hexarelin is not an approved drug and is sold as a research chemical, labeled research use only and not for human consumption. Because no regulator oversees how it is made, what is in a given vial is whatever the synthesis and the seller's quality control produced. That puts the burden on independent verification. A meaningful certificate of analysis identifies the actual peptide and reports purity, usually by HPLC for purity and mass spectrometry for identity, ideally from a lab with no stake in the sale. peptideone does not test or sell anything; we aggregate public COAs and the third-party raters covering this market so the documentation can be compared in one place.
Nothing here is medical or dosing advice.