Hexarelin

Hexarelin is a synthetic hexapeptide growth hormone secretagogue that activates the ghrelin receptor. It has been studied in small human studies of growth hormone release and in cardiovascular research, and is not approved for any use.

Last reviewed 2026-10-25 by the PeptideWiki editorial team. Editorial policy.

Overview

Hexarelin, also known by the international nonproprietary name examorelin, belongs to the family of synthetic growth hormone-releasing peptides (GHRPs) developed before the discovery of ghrelin. It is closely related in structure to GHRP-6 and stimulates growth hormone release from the pituitary by activating the growth hormone secretagogue receptor, later shown to be the receptor for ghrelin. In early human studies it was among the more potent members of this group for acute growth hormone release.

Research on hexarelin extended beyond the growth hormone axis. Studies in animals and isolated hearts reported cardiovascular effects that appeared partly independent of growth hormone, leading to the identification of the scavenger receptor CD36 as an additional binding site. Human studies were small and mainly short-term, covering endocrine testing and cardiac function measures. The compound did not proceed to approval and remains a research tool in endocrinology and cardiovascular pharmacology.

Structure

Hexarelin is a linear hexapeptide with the sequence His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH₂. It differs from GHRP-6 mainly by the use of 2-methyl-D-tryptophan in place of D-tryptophan at position 2. It includes two D-amino acids, which slow enzymatic degradation, and a C-terminal amide. The two tryptophan-derived residues make it susceptible to oxidation. It is generally supplied as a lyophilized acetate or trifluoroacetate salt.

Mechanism

Hexarelin is an agonist of the growth hormone secretagogue receptor type 1a (GHS-R1a), the ghrelin receptor, which is expressed in the pituitary and hypothalamus. Activation stimulates growth hormone secretion and acts synergistically with growth hormone-releasing hormone. Like other GHRPs, hexarelin can also raise prolactin and adrenocorticotropic hormone and cortisol to some extent. Repeated exposure in studies was associated with partial attenuation of the growth hormone response.

Hexarelin also binds CD36, a scavenger receptor found on cardiomyocytes, macrophages and other cells. Cardioprotective effects observed in rodent and isolated heart models have been attributed in part to this interaction, but the significance of CD36 binding in people is not established.

Research

Growth hormone release in humans

Small clinical pharmacology studies in the 1990s examined hexarelin's ability to stimulate growth hormone release in healthy volunteers, older adults and children with short stature. These studies characterized acute growth hormone responses, interaction with growth hormone-releasing hormone, and effects on prolactin and cortisol. They also reported that responses can diminish with repeated administration. The work is useful for understanding ghrelin receptor physiology but does not establish any clinical benefit.

Cardiovascular research

In rodent models of myocardial ischemia and in isolated heart preparations, hexarelin was reported to have protective effects on cardiac function, some of which occurred in animals lacking growth hormone, implicating a direct cardiac mechanism. Small human studies measured acute changes in cardiac function indices. These observations led to research on CD36 as a target, but the clinical relevance of the findings remains uncertain.

Receptor pharmacology

Hexarelin has been used as a pharmacological tool to study the ghrelin receptor and to distinguish ghrelin receptor effects from those mediated by CD36. Binding and functional studies in cell systems and tissue preparations have helped map the receptor's signaling and its desensitization. This laboratory work is a main ongoing use of the compound. Comparisons with other ghrelin receptor agonists, including GHRP-6 and nonpeptide secretagogues, have helped clarify structure-activity relationships within this class.

Evidence quality

Human data for hexarelin come from small, mostly short-term studies conducted decades ago. Long-term safety and efficacy in any condition have not been established, and the compound was not carried forward to approval. Its cardiovascular findings are largely preclinical. It should be regarded as an investigational research peptide. Modern studies, where they exist, are mostly laboratory investigations of receptor binding and cardiac signaling rather than clinical trials.

Regulatory status

Hexarelin is not approved by the FDA for any use. It is not a recognized substance for US pharmacy compounding. WADA prohibits growth hormone secretagogues and ghrelin mimetics, including hexarelin, at all times under class S2.

Status changes often. See the regulatory tracker for dated updates.

Quality and identity testing

A certificate of analysis should confirm identity by mass spectrometry against the expected mass shown on this page and report reverse-phase HPLC purity with the chromatogram. The two tryptophan-type residues are prone to oxidation, producing +16 and +32 Da species, which should be monitored as related substances. Because the D-configuration at positions 2 and 5 is essential, diastereomeric impurities may be present and are not distinguished by mass alone; chiral or high-resolution HPLC methods help. Confusion with GHRP-6, which differs by a methyl group (about 14 Da), is a further identity check. Counter-ion and net peptide content should be stated.

For a walkthrough of each section of a certificate, see how to read a COA.

Storage and stability

Store lyophilized hexarelin sealed at -20 °C or colder, protected from light and moisture, because the tryptophan-derived residues are sensitive to photo-oxidation. Allow vials to reach room temperature before opening to avoid condensation. Solutions for lab use should be prepared in sterile, preferably degassed water or buffer, kept refrigerated for short-term work, aliquoted for longer storage at -20 °C or below, and not subjected to repeated freeze-thaw cycles.

Download the Hexarelin data sheet (PDF): sequence, masses, expected MS ions and handling on one printable page.

Latest research

Frequently asked questions

Related compounds

• GHRP-6

  GHRP-6 is a synthetic hexapeptide that stimulates growth hormone release by activating the ghrelin receptor (GHS-R1a). It was one of the first growth hormone secretagogues and is not approved for any use.

• GHRP-2

  GHRP-2 (pralmorelin) is a synthetic hexapeptide that stimulates growth hormone release by activating the ghrelin receptor. It has been studied in human endocrine testing and is not approved by the FDA.

• Ipamorelin

  Ipamorelin is a synthetic pentapeptide growth hormone secretagogue that acts as a selective agonist of the ghrelin receptor (GHS-R1a). It is investigational and not approved for any use.

• MK-677 (ibutamoren)

  MK-677 (ibutamoren) is an orally active small-molecule agonist of the ghrelin receptor that raises growth hormone and IGF-1 levels. It is not a peptide, and it is not approved for any use.

References

1. PubMed: all indexed literature on Hexarelin
2. ClinicalTrials.gov: registered studies mentioning Hexarelin