Prepared by: Research Desk
Prepared by: Research Desk. Sources are linked for verification.
Hexarelin (also called examorelin) is a synthetic peptide of six amino acids. It belongs to the growth-hormone-releasing peptide (GHRP) family, a group of small synthetic molecules that cause the pituitary gland to release growth hormone (GH) through a different receptor from the one used by growth-hormone-releasing hormone (GHRH). Most of its published record comes from human endocrine pharmacology studies in the 1990s and early 2000s, followed by a body of animal and cell research on the heart, blood vessels and lipid metabolism [1].
This entry follows the standard Peptide Infinity template: identity, mechanism, status, key evidence, then sources.
Status at a glance
Field | Entry |
|---|---|
Other names | Examorelin |
Class | Synthetic growth-hormone secretagogue (GHRP family) |
Length | 6 amino acids (hexapeptide), C-terminal amide |
Main receptors studied | GHS-R1a (the ghrelin receptor); CD36 scavenger receptor |
U.S. status | Unapproved / no recognized status (no FDA-approved product identified as of 23 October 2026) |
Sport | Prohibited at all times under WADA class S2 |
Evidence base | Small human endocrine studies; animal and cell studies |
For what each status label means in U.S. law, see Peptide FDA status explained.
Identity and structure
Hexarelin's sequence is His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2. Two features stand out to chemists:
D-amino acids. Two residues are in the D-configuration, the mirror image of the L-amino acids found in natural proteins. D-residues generally make a short peptide harder for enzymes to cut.
A methylated D-tryptophan. The second residue is a D-tryptophan carrying a methyl group at position 2 of its indole ring. This single change is what distinguishes hexarelin from the earlier hexapeptide GHRP-6, which has an unmodified D-tryptophan at the same position.
The C-terminus ends in an amide (-NH2) rather than a free carboxylic acid, another common modification in synthetic peptides. Readers new to residue notation can start with What are peptides?, and terms such as agonist and secretagogue are defined in the peptide glossary.
A close structural relative is alexamorelin, which is the hexarelin sequence with one extra alanine added at the N-terminus (Ala-His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2). A human study of alexamorelin measured the same set of hormones used in hexarelin research: GH, prolactin, ACTH and cortisol [2].
Mechanism: two receptors in the literature
GHS-R1a, the ghrelin receptor
Hexarelin was designed before the body's own ligand for this pathway was known. GHRPs act on the growth hormone secretagogue receptor type 1a (GHS-R1a), later identified as the receptor for the stomach-derived hormone ghrelin. Binding at the pituitary and hypothalamus is the basis of its GH-releasing action [1].
Binding studies also looked beyond the brain. A 2000 study mapped GHS binding sites in peripheral human tissues, reporting binding in several organs outside the pituitary, including cardiovascular tissue [3]. Findings like this prompted researchers to ask whether hexarelin had actions independent of GH release.
CD36, a scavenger receptor
A 2002 study in Circulation Research identified CD36, a scavenger receptor best known for handling fatty acids and oxidized lipids, as a cardiac binding site for growth-hormone-releasing peptides, and reported that CD36 mediated their cardiovascular action in the heart [4]. This laboratory work is the main reason hexarelin appears in cardiovascular research separately from its endocrine role. Reviews of the field describe these heart effects as acting at least partly through receptors other than GHS-R1a [1].
What human endocrine studies measured
Human research on hexarelin was largely endocrine pharmacology: short, small studies that gave the compound under controlled conditions and measured hormone levels in blood. They were designed to map how the hormone system responds, not to test a medical use. Key themes:
Growth hormone. GH release was the primary readout, and hexarelin served as a reference GH secretagogue in several comparative studies [1][2].
Prolactin, ACTH and cortisol. Like other GHRPs, hexarelin was reported to raise prolactin and to activate the hypothalamo-pituitary-adrenal (HPA) axis. A 1999 study reported that hexarelin stimulated the HPA axis in humans via arginine vasopressin, rather than solely through corticotropin-releasing hormone [5].
Interaction with inhibitory peptides. A 2003 study tested whether cortistatin-14 and somatostatin-14, two related inhibitory neuropeptides, altered the endocrine response to hexarelin in human volunteers, measuring GH alongside prolactin, ACTH and cortisol [6]. Both inhibitory peptides were reported to blunt the GH response.
Attenuation with repeated exposure. Review literature notes that the GH response to hexarelin was reported to diminish partially during prolonged exposure, a pattern described as desensitization or tachyphylaxis [1].
Outside the pituitary, a 2002 cell study reported that hexarelin stimulated GH release from human peripheral lymphocytes in vitro [7]. This is a laboratory observation on isolated cells and does not show what happens in the whole body.
Animal and cell research
Most post-2000 hexarelin papers are animal studies. They report what was measured in specific models; none establishes an effect in humans.
Heart injury model (rat). A 2017 study reported that hexarelin protected rat cardiomyocytes from in vivo ischemia/reperfusion injury and linked the effect to interleukin-1 signaling [8].
Atherosclerosis model (rat). A 2010 study used rats fed a high-lipid diet with vitamin D3 to induce atherosclerosis and reported that hexarelin suppressed lesion development in that model [9].
Lipid metabolism (mouse). A 2017 study in nonobese, insulin-resistant male MKR mice reported changes in lipid metabolic measures after hexarelin exposure [10].
Reviews. A 2014 review summarized the cardiovascular research [1], and a 2015 review discussed ghrelin and hexarelin in the context of diabetes and diabetes-associated heart disease [11].
Animal models differ from humans in receptor distribution, metabolism and disease biology. The evidence checklist explains why animal and cell findings sit low on the evidence ladder.
Regulatory and sport status
United States. Peptide Infinity found no FDA-approved drug product containing hexarelin when this entry was checked, so it carries the Unapproved / no recognized status label. FDA separately maintains lists of bulk drug substances that pharmacies may or may not use in compounding under section 503A, and those lists change over time [13]. Readers checking any substance's compounding position should consult the current FDA page directly.
Sport. The World Anti-Doping Agency Prohibited List includes growth hormone secretagogues and growth-hormone-releasing peptides under class S2 (peptide hormones, growth factors, related substances and mimetics), prohibited at all times; hexarelin is among the named examples [12]. The list is updated annually, so the current edition is the reference.
How hexarelin compares with related entries
Hexarelin works through the ghrelin-receptor pathway. Sermorelin and tesamorelin are GHRH analogues that act on a different receptor, the GHRH receptor. Sermorelin was once an FDA-approved product that is no longer marketed, and tesamorelin has an FDA approval for a specific indication; see the sermorelin and tesamorelin entries. For background on how peptide hormones signal compared with steroid hormones, see Peptide hormones.
Frequently asked questions
Is hexarelin the same as ghrelin?
No. Ghrelin is a natural 28-amino-acid hormone, while hexarelin is a synthetic six-residue peptide. Both act on the GHS-R1a receptor, but hexarelin was also studied for binding at the CD36 scavenger receptor in heart tissue [4].
Is hexarelin FDA approved?
No FDA-approved product containing hexarelin was identified as of 23 October 2026. Its published record consists of human endocrine pharmacology studies and animal and cell research [1].
Why is hexarelin on the WADA Prohibited List?
WADA class S2 covers substances that release growth hormone, including growth-hormone-releasing peptides such as hexarelin [12]. They are prohibited both in and out of competition.
What did human studies of hexarelin measure?
They measured blood levels of growth hormone, prolactin, ACTH and cortisol under controlled conditions, and examined how inhibitory neuropeptides and repeated exposure changed those responses [5][6].
Further reading
A good reference textbook gives the receptor biology and hormone physiology behind entries like this one in more depth than a single article can. When comparing titles, check the edition year first: receptor pharmacology has moved quickly since the early 2000s, and older editions may predate key discoveries.
Other neutral criteria worth weighing: whether the authors cite primary literature chapter by chapter, whether the book covers both chemistry and physiology, the format (print, e-book or both) and whether the publisher lists a transparent price and table of contents before purchase.
Introductory readers often do best with a general endocrinology or medicinal chemistry text, while advanced readers may prefer a specialist monograph on receptor signaling. Library copies and publisher sample chapters are a low-cost way to judge depth and readability first.
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Last updated: 23 October 2026.
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