— Research note —
Hexarelin
Hexapeptide ghrelin receptor agonist investigated as a potent growth hormone secretagogue with cardiovascular research interest.
Hexarelin is a synthetic hexapeptide (His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2) developed by the Deghenghi group at Europeptides in the late 1980s and early 1990s as a member of the growth hormone-releasing peptide (GHRP) class. Structurally derived from GHRP-6 by methyl substitution of the tryptophan residue, hexarelin exhibits enhanced potency at the growth hormone secretagogue receptor and improved enzymatic stability, supporting use in both subcutaneous and oral administration research protocols.
The compound has been one of the most extensively characterized GHRP-class molecules in clinical research, with phase 1 and phase 2 studies in pediatric growth disorders, adult growth hormone deficiency, and cardiovascular research applications. A notable thread of hexarelin research concerns cardiovascular pharmacology: the compound has been shown to bind a distinct CD36-related receptor in cardiac tissue, with preclinical studies reporting cardioprotective effects in ischemia-reperfusion models that appear partially independent of growth hormone release.
In growth hormone axis studies, hexarelin produces a robust growth hormone pulse comparable to or exceeding that of GHRP-6 and GHRP-2 on a milligram-equivalent basis. Like other GHRPs, the molecule synergizes with GHRH analogs to produce growth hormone responses that exceed the simple sum of individual peptide effects. Hexarelin's potency has made it a benchmark tool compound for ghrelin receptor pharmacology and for structure-activity studies of the GHRP scaffold.
The compound is supplied here for laboratory research use only and is not intended for human consumption. Researchers have used hexarelin as a probe in pituitary pharmacology, cardiac receptor biology, and the ongoing characterization of non-canonical ghrelin receptor signaling.
Mechanism
Hexarelin engages the growth hormone secretagogue receptor type 1a (GHSR-1a) on pituitary somatotrophs and hypothalamic neurons, activating Gq-mediated phospholipase C signaling and elevating intracellular calcium to stimulate growth hormone secretion. The methylated tryptophan residue at position 2 enhances receptor binding affinity and provides resistance to proteolytic degradation relative to GHRP-6.
A distinguishing feature of hexarelin pharmacology is its reported binding to CD36, a class B scavenger receptor expressed in cardiac myocytes, macrophages, and other tissues. This interaction has been proposed to mediate cardioprotective effects observed in ischemia-reperfusion models, including preservation of left ventricular function and reduction of infarct size. The cardiac actions of hexarelin appear partially distinct from its growth hormone-releasing properties, providing a rationale for ongoing research into the broader pharmacology of CD36-targeted peptides.
Research history
Hexarelin was developed by Romano Deghenghi and colleagues at Europeptides in the late 1980s as part of a structure-activity series exploring methylated derivatives of GHRP-6. The compound entered clinical research in the early 1990s with investigations of growth hormone responses in healthy adults, children with short stature, and adults with growth hormone deficiency.
Italian research groups, including those associated with the University of Turin, characterized the pharmacological profile in extensive published series during the 1990s and 2000s. The identification of cardiac CD36 binding and cardioprotective effects in ischemia-reperfusion models emerged from research by the Locatelli and Berti groups in the early 2000s, opening a parallel research direction beyond growth hormone biology.
Subsequent academic research has examined hexarelin in models of cachexia, sarcopenia, and metabolic regulation, often in comparison with other GHRPs and with the endogenous ligand ghrelin. The compound has been frequently used in pharmacological characterization of GHSR-1a signaling and as a positive control in receptor binding assays. Hexarelin continues to appear in research-chemical catalogs as a high-potency reference compound for the GHRP class.
References
- Deghenghi R, et al. 1994. GH-releasing activity of Hexarelin, a new growth hormone releasing peptide, in infant and adult rats. Life Sci. PMID: 8208173
- Locatelli V, et al. 1999. Growth hormone-independent cardioprotective effects of hexarelin in the rat. Endocrinology. PMID: 10220994
- Bisi G, et al. 1999. Acute cardiovascular and hormonal effects of GH and hexarelin, a synthetic GH-releasing peptide, in humans. J Endocrinol Invest. PMID: 10076717
- Demers A, et al. 2004. Identification of the growth hormone-releasing peptide binding site in CD36: a photoaffinity cross-linking study. Biochem J. PMID: 14741043
- Smith RG. 2005. Development of growth hormone secretagogues. Endocr Rev. PMID: 15814848
- Mao Y, et al. 2014. Hexarelin treatment in male ghrelin knockout mice after myocardial infarction. Endocrinology. PMID: 25033140
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Information presented in third-person scientific context. Research use only. Not medical advice; not for human consumption.