Hexarelin Peptide

## What it is Hexarelin (examorelin) is a synthetic hexapeptide growth-hormone secretagogue developed in the 1990s by Italian biotechnology firm Mediolanum (subsequently acquired into Pfizer's pipeline). The sequence (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) was engineered as an analog of GHRP-6 with a methylated tryptophan to resist enzymatic cleavage. It produces the largest acute GH pulse of the synthetic GHRP class at equivalent molar doses, and was advanced through phase 2 trials in adult GH deficiency and pediatric short stature in the late 1990s and early 2000s before development was discontinued. The compound has no FDA, EMA, or PMDA approval. Italian and European regulators evaluated it in clinical trials but it never reached registration. WADA places hexarelin on the Prohibited List under S2 (peptide hormones, growth factors). Distribution is via research-peptide vendors and the user base is small relative to GHRP-2 and ipamorelin, predominantly limited to users specifically chasing maximum acute GH amplitude. A distinguishing feature: hexarelin has independent activity at CD36, a scavenger receptor expressed in cardiac tissue, vascular endothelium, and macrophages. This produces cardioprotective signaling in rodent infarct models that is largely independent of the GH response, and has driven a parallel research thread distinct from the body-composition use case. ## Mechanism of action Hexarelin binds GHS-R1a (the ghrelin receptor) with high affinity, suppressing hypothalamic somatostatin and stimulating pituitary somatotrophs. The acute GH pulse is dose-dependent and substantially larger than GHRP-2 or GHRP-6 at the same molar dose. Like other GHRPs, hexarelin produces measurable cortisol and prolactin release through hypothalamic-pituitary cross-talk; this profile is more pronounced than GHRP-2 and substantially more pronounced than ipamorelin. The CD36 signaling is the structural distinguishing feature. Bodart 2002 demonstrated cardioprotective effects of hexarelin in rat ischemia-reperfusion injury that were preserved in GH-deficient animals, indicating GH-independent cardiac action via CD36. Subsequent rodent work has reported reduced infarct size, improved post-MI ejection fraction, and modulation of macrophage polarization in atherosclerosis models. Plasma half-life is short, on the order of 30 to 60 minutes. Subcutaneous injection produces a GH peak within 15 to 30 minutes that returns to baseline within 2 to 3 hours. Repeated daily dosing in early human trials showed progressive desensitization of the GH pulse over 2 to 4 weeks, an effect more pronounced than seen with GHRP-2 or ipamorelin and a structural reason chronic dosing protocols lose efficacy faster. ## Evidence base Human trial data is the most substantial of any GHRP outside ipamorelin. Mediolanum and academic collaborators ran phase 1 and 2 trials in healthy adults, adult GH deficiency, and pediatric short stature totaling several hundred participants across studies. Imbimbo 1994 and Ghigo 1994 documented acute GH provocation profiles. A pediatric short-stature trial (Mericq 1998) reported modest growth velocity gains over 6 months; the program did not progress to phase 3 registration. The critical clinical concern that emerged from chronic-dosing studies was tachyphylaxis: the GH response progressively attenuates over weeks of daily dosing, more rapidly than with other GHRPs. This pharmacologic property limited clinical development and is a structural reason why most users today cycle hexarelin tightly or pair it with GHRH analogs to preserve responsiveness. The cardioprotection literature is preclinical. Approximately 10 to 15 rodent studies report reduced infarct size, improved post-ischemic ejection fraction, and anti-inflammatory effects in cardiac tissue, mediated by CD36 rather than GH. No completed human cardiovascular trial of hexarelin exists. ## Dosage and administration Research-protocol dosing typically runs 100 to 200 mcg subcutaneously 1 to 2 times daily, often timed pre-bed and post-workout to align with endogenous GH pulse windows. Doses above 200 mcg produce larger acute GH pulses but accelerated tachyphylaxis. Most experienced users limit hexarelin cycles to 2 to 4 weeks given the receptor desensitization, then rotate to GHRP-2 or ipamorelin for an extended off-period. A typical 5 mg vial reconstituted with 2 mL bacteriostatic water gives 2.5 mg/mL. A 100 mcg dose draws 4 units on a U100 insulin syringe. Hexarelin is occasionally stacked with CJC-1295 no-DAC at the same time point on the rationale of synergistic GH release through parallel pathways, with the caveat that the GH-axis cortisol load is higher than with ipamorelin pairings. Fasted dosing with a 30 minute window before food is the standard protocol; circulating glucose and free fatty acids suppress GH release. ## Side effects and safety The most pronounced side effects relative to other GHRPs are cortisol and prolactin elevation; users with prolactin sensitivity (gynecomastia history, libido changes) report issues more commonly than with ipamorelin. Other reported effects include water retention, vivid dreams, head pressure or flushing, transient lethargy, and tingling at the injection site. The hunger response is moderate, less pronounced than GHRP-6 and roughly comparable to GHRP-2. Long-term safety in humans is not characterized at chronic-use doses. The accelerated tachyphylaxis observed in human trials is itself a safety-relevant finding because it implies users seeking sustained response may escalate doses with diminishing efficacy and amplifying cortisol load. Theoretical concerns include sustained GH-induced insulin resistance, theoretical malignancy concern via IGF-1 axis, and ACTH-driven cortisol elevation if dosing is excessive. Contraindications on mechanistic grounds include pregnancy, active malignancy, history of pituitary tumor, uncontrolled diabetes, and prolactin-sensitive states. Athletes face WADA sanctions; detection methods are validated for hexarelin metabolites. ## Practical notes Lyophilized hexarelin is stable at room temperature for the labeled shelf life and should be refrigerated for longer storage. Reconstituted vials should be refrigerated and used within 4 weeks. Bacteriostatic water is the standard reconstitution medium. The acute GH pulse is the largest of the synthetic GHRPs, which is the practical reason users select hexarelin over alternatives. The downside is tachyphylaxis: by week 3 to 4 of daily dosing the GH pulse is materially smaller than week 1, and the cortisol and prolactin tail does not attenuate to the same degree, so the dose-response profile worsens over time. Most experienced users run 2 to 4 week pulses with extended off-periods rather than continuous dosing. For users specifically interested in the CD36-mediated cardiac signaling, the honest framing is that the rodent data is interesting and the human data is essentially absent. Treat the cardioprotection narrative as preclinical hypothesis rather than clinical evidence.