Hexarelin

Hexarelin is best understood as the older, blunter sibling of ipamorelin. It came earlier, it releases more GH per microgram, and it was studied across a wide range of patient groups (children with short stature, healthy adults, elderly subjects, GH-deficient patients). But it never won approval. The reasons it lost out to newer GHRPs are the same reasons it sits at evidence grade D today: it is less selective (it bumps cortisol and prolactin), it shows clear tachyphylaxis (the GH response shrinks with repeated dosing), and the clinical case for using it never crystallised before pharma interest moved on.

Hexarelin has a real, but limited and aged, clinical evidence base. The foundational work is from the mid-1990s: Imbimbo et al. 1994 (the human dose-response IV study) and Ghigo et al. 1994 (the multi-route paper showing oral, intranasal and SC activity). Across these and follow-ups (Loche et al. 1997, Massoud et al. 1996), hexarelin reliably produces a large acute GH pulse, larger per microgram than GHRH or ipamorelin in head-to-head settings. But the same body of work also surfaces the problems that ended its development: cortisol and prolactin rises in most subjects, ACTH co-stimulation, and clear receptor desensitisation with daily dosing. The "elderly subjects" series (Arvat et al. 1994, Ghigo et al. 1996) showed an age-related blunting of the response, undermining the obvious anti-ageing pitch. There are no large phase 2/3 outcome trials, no controlled body-composition data, and no modern safety surveillance. Almost everything you read about hexarelin in performance contexts is extrapolated from 30-year-old single-dose endocrinology, not new clinical evidence.

No approved human protocol exists and no safe or effective dose has been established for any non-investigational use. The classic Imbimbo 1994 dose-response used single IV doses of 0.25 to 2 µg/kg in healthy adults; Ghigo 1994 tested 1.5 µg/kg IV, 1.5 µg/kg SC, 20 µg/kg intranasally and 60 to 80 µg/kg orally as single doses. These were pharmacology experiments, not therapeutic regimens. Subcutaneous protocols described in bodybuilding and research-peptide communities (typically 100 to 200 µg, sometimes multiple times per day) are not backed by clinical evidence and the purity of "research peptide" vials is not regulated. A qualified clinician should be consulted before considering any peptide.

In short-duration human studies, hexarelin was generally tolerated but its side-effect profile is materially worse than newer selective GHRPs. The most consistent issues are transient rises in cortisol, prolactin and ACTH at GH-releasing doses, flushing, and occasional headache. The lack of selectivity is not a theoretical concern; it shows up in almost every endocrinology paper on the molecule. The tachyphylaxis problem (the GH response shrinking within days of repeated dosing) is well documented and is one of the reasons it never advanced as a chronic therapy. Long-term safety in healthy adults using hexarelin for performance reasons is essentially unknown, with no multi-month controlled trials. The general GH/IGF-1 axis cautions apply: theoretical risk of worsened insulin resistance, fluid retention, accelerated diabetic retinopathy, and growth of pre-existing tumours (IGF-1 is mitogenic). Products sold as "hexarelin" online are unregulated research chemicals with no purity or sterility guarantee.