Hexarelin

Origin and Structure

Hexarelin (also called examorelin) is a synthetic hexapeptide with the sequence His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH₂ — essentially a methylated analogue of GHRP-6. The 2-methyl substitution on D-tryptophan dramatically increases metabolic stability and receptor binding, and the compound was developed in the early 1990s in Italy by Europeptides (later Mediolanum Farmaceutici) as a more potent and longer-acting GHRP. Hexarelin advanced through Phase 2 clinical work on several indications in the late 1990s but was not brought to approval.

Mechanism of Action

Hexarelin binds the ghrelin receptor (GHSR-1a) on pituitary somatotrophs to drive pulsatile GH release, with potency comparable to or exceeding GHRP-2 in most head-to-head pharmacodynamic studies. Its distinguishing mechanistic feature is activity at a second, non-GHSR receptor — specifically CD36, a class B scavenger receptor expressed heavily in cardiac tissue, macrophages, and adipose.

Hexarelin's CD36 binding is the basis for a substantial body of cardiovascular research that has no parallel elsewhere in the GHRP class. Preclinical and small clinical studies have reported cardioprotective effects in ischemia-reperfusion models, improvements in left-ventricular function in rats with experimentally induced heart failure, and vasodilatory effects in isolated vessels — all apparently independent of GH release. Whether these effects translate to clinical cardiology in humans remains unresolved, but the mechanistic signal has sustained research interest for three decades.

Clinical Evidence

Human trials with hexarelin have included:

• GH stimulation testing. Intravenous and subcutaneous hexarelin were validated as GH-response probes in academic work comparable to other GHRPs.
• GH deficiency treatment. Phase 2 trials in GH-deficient children and adults showed GH and IGF-1 elevations but also demonstrated the class-wide problem of receptor desensitization with continuous daily dosing — by 16 weeks, GH response was significantly attenuated.
• Cardiovascular studies. Small trials in dilated cardiomyopathy and post-MI patients reported functional improvements, though these were pilot-scale and have not been replicated in adequately powered trials.

The desensitization problem is meaningful: hexarelin's potency advantage over other GHRPs erodes quickly with chronic dosing, which is why short cycles (typically 4-8 weeks) are the norm in research-use protocols.

Practical Considerations

Research-use doses are typically 100-200 mcg subcutaneously, two or three times daily, fasted. Cycling is essentially mandatory — unlike ipamorelin or the GHRH analogues, sustained hexarelin dosing will produce diminishing returns within weeks. Protocols commonly include 4-8 weeks on followed by equal or longer washouts. Hexarelin is sometimes rotated with ipamorelin within a longer GH-peptide cycle to preserve response.

Cortisol and prolactin increases are real with hexarelin, intermediate between GHRP-2 and GHRP-6 in most comparative studies. Appetite stimulation is modest — less prominent than with GHRP-6 but greater than with ipamorelin.

Safety and Regulatory Status

Commonly reported side effects include injection-site reactions, transient flushing, tingling or numbness, mild headache, and water retention. The cardioprotective CD36 activity is double-edged: a 2001 study flagged myocardial hypertrophy in rats given high chronic doses, which remains a theoretical long-term concern with sustained use in humans. Long-term cardiac safety data in humans does not exist.

Hexarelin is not FDA-approved for any indication. It is on the WADA prohibited list (class S2). It is supplied through research-chemical vendors and compounding pharmacies, and its niche among GH-releasing peptides is firmly that of a short-cycle, high-potency tool compound rather than a long-term therapeutic. For a broader look at the recovery-peptide category, see our recovery peptide guide.