The GHRP engineered for maximum potency
Hexarelin was synthesised by Mediolanum Farmaceutici in Milan in 1972, building on Cyril Bowers' discovery that enkephalin analogues could stimulate GH release. It is a hexapeptide (6 amino acids: His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2), where the critical innovation is the D-2-methyl-Tryptophan substitution — this modification gives hexarelin its exceptional potency and resistance to enzymatic degradation relative to its parent compound GHRP-6.
The foundational 1994 Ghigo clinical study established hexarelin as the most potent GH secretagogue in its class by a substantial margin. At 1-2 μg/kg IV in healthy volunteers, hexarelin elicited robust GH peaks via multiple routes including intravenous, subcutaneous, intranasal, and oral. The Phase II clinical programme explored both GH deficiency diagnosis and cardiac indications — ultimately discontinued for commercial reasons rather than safety failures.
The discovery of hexarelin's cardiac receptor (CD36) by Papotti et al. (2000) and Bodart et al. (2002) transformed understanding of the GHRP family. CD36, an 88 kDa glycoprotein on cardiomyocytes and microvascular endothelial cells, is not a GH receptor — it is a scavenger receptor involved in fatty acid transport and cellular signalling. Hexarelin's binding to CD36 in cardiac tissue produces cardioprotective effects that persist even in hypophysectomised animals with no pituitary GH response. The heart has its own hexarelin receptor that operates completely separately from the pituitary axis.
Hexarelin vs Ipamorelin: Hexarelin is the most potent GHRP; ipamorelin is the most selective. Hexarelin elevates cortisol and prolactin alongside GH — ipamorelin does not. For pure GH optimisation with the cleanest side effect profile, ipamorelin is generally preferred. For maximum GH output or cardiac applications, hexarelin's unique profile becomes relevant. Choose based on your goals and tolerance for the cortisol/prolactin effects.