Hexarelin

Hexarelin (also designated Examorelin, developmental code EP-23905) is a synthetic, six-amino-acid peptide belonging to the growth hormone-releasing peptide (GHRP) family. It was developed in the early 1990s through structure-activity optimization of met-enkephalin analogs, specifically to maximize GH release via ghrelin receptor (GHS-R1a) agonism. Unlike endogenous ghrelin, hexarelin does not carry the acyl side chain and does not meaningfully stimulate appetite or alter gastric motility at research doses, which has made it a cleaner tool for isolating GH-axis effects in preclinical work. It is classified as a research chemical in all major jurisdictions and is not approved for human use by the FDA, MHRA, EMA, or TGA. This content is for educational purposes only and does not constitute medical advice.

Hexarelin's primary mechanism involves agonism at the ghrelin receptor (GHS-R1a), located in the hypothalamus and pituitary, triggering pulsatile growth hormone release. This action is synergistic with endogenous GHRH, meaning co-administration with a GHRH analog in animal studies consistently produces amplified GH pulses. What distinguishes hexarelin from most other GHRPs is evidence of direct cardiac receptor binding, specifically at CD36 scavenger receptors expressed on cardiomyocytes and vascular smooth muscle. Research in animal models suggests this CD36 pathway mediates cardioprotective effects independent of GH secretion itself — an observation that has attracted cardiovascular research interest beyond the GH axis. The mechanism here is thought to involve anti-apoptotic signaling and reduced ischemia-reperfusion injury, though this remains primarily animal-model data.

Evidence base: The strongest hexarelin data comes from animal models and a limited but notable set of human trials. In human studies conducted in the 1990s and early 2000s (primarily Italian and European research groups), hexarelin was shown to stimulate robust GH secretion in healthy volunteers and in patients with GH deficiency, with single-dose IV and subcutaneous administrations producing measurable IGF-1 elevation. A frequently cited study by Ghigo et al. (1994) demonstrated dose-dependent GH release in healthy adults. Crucially, multiple human trials documented rapid desensitization with repeated dosing — GH response was significantly attenuated within 2-4 weeks of continuous administration, a finding that distinguishes hexarelin from lower-efficacy GHRPs like ipamorelin, which show less tachyphylaxis. Animal studies (rodent and porcine cardiac models) suggest cardioprotective effects following ischemic injury, including improved left ventricular function and reduced infarct size. These cardiac findings have not been replicated in adequately powered human trials. User-reported anecdotal data from bodybuilding and biohacking communities describes pronounced GH pulses, increased appetite (at higher doses), and significant water retention — but these are uncontrolled self-reports and carry no evidentiary weight.

Dosing ranges reported in research contexts: Human trial doses in published studies have generally ranged from 1 mcg/kg to 2 mcg/kg administered subcutaneously or intravenously, typically as single or twice-daily injections. Some protocols examined doses up to 100 mcg per administration. Animal cardiac studies have used weight-adjusted IV doses outside any practical human-equivalent frame. These ranges are reported here strictly as observed in published research — they are not a recommendation for any dosing regimen, and hexarelin is not approved for human use. Reconstitution from lyophilized powder is required; bacteriostatic water is the standard diluent in research settings. Reconstituted product requires refrigeration and is typically considered stable for 2-4 weeks under refrigeration.

Legal status and sourcing: Hexarelin occupies a gray-area 'research chemical' status in the US, UK, and EU — it is not scheduled as a controlled substance but is not approved for human consumption. In Australia, it falls under Schedule 4 (prescription-only) or Schedule 9 depending on context, making unsanctioned possession more legally consequential. Credible research-chemical vendors will provide third-party mass spectrometry or HPLC certificates of analysis (COAs); any vendor unwilling to share COA documentation on request should be avoided. Purity benchmarks for legitimate research applications are typically ≥98% by HPLC. Hexarelin is subject to WADA prohibition as a peptide hormone and is banned in competitive sport.