Peptide Evidence Index

Hexarelin

Evidence last reviewed: September 2026

Quick answers

What is it?: Hexarelin is a fully synthetic chain of six amino acids designed to trigger the same receptor as the natural hunger hormone ghrelin, causing the pituitary gland to release a pulse of growth hormone. It is not approved as a medicine anywhere and is sold only as an unregulated research chemical.
Why are people interested in it?: It's marketed today for muscle building, fat loss, and anti-aging, so people want to know what its actual, decades-old human research shows.
What has actually been studied?: A single Turin, Italy research group ran small studies in the late 1990s and early 2000s giving healthy volunteers, usually six at a time, single or short courses of hexarelin and measuring hormone changes; the same group also gave a single dose to 24 coronary artery disease patients during heart bypass surgery.
How strong is the evidence?: Early human data only: small, uncontrolled or mechanistic studies measuring acute hormone or cardiac responses, not a single outcome trial testing hexarelin as a treatment for anything.
What don't we know yet?: Whether recent animal findings on heart, brain, and blood vessel protection translate to humans, and whether hexarelin does anything for muscle, fat, or recovery in healthy adults — this has never been tested.
Where can I read the original research?: Sources at the bottom of this page: Effects of acute hexarelin administration on cardiac performance in patients with coronary artery disease during by-pass surgery, European Journal of Pharmacology 2002; Maccario et al., European Journal of Endocrinology 2002.

Plain-English overview

Hexarelin is a fully synthetic chain of six amino acids engineered to activate the growth hormone secretagogue receptor, the same receptor the body's natural hunger hormone ghrelin acts on. It has never been approved as a medicine anywhere, development as a growth-hormone therapeutic was abandoned decades ago, and it is sold only as an unregulated research chemical, prohibited at all times in competitive sport. Its human research record is real but narrow and old: a single research group in Turin, Italy published a series of small studies in the late 1990s and early 2000s giving healthy volunteers, usually six at a time, single or short courses of hexarelin and measuring what happened to their growth hormone, ACTH, cortisol, and prolactin. The same group separately gave a single intravenous dose to 24 men with coronary artery disease during heart bypass surgery and measured an acute, short-lived improvement in cardiac output. None of these studies tested hexarelin as a treatment for anything; they measured acute hormonal or cardiovascular responses, not outcomes. No trial of hexarelin is registered on ClinicalTrials.gov, and no human study has ever tested it for the muscle-building, fat-loss, or anti-aging uses it is marketed for today.

What researchers are studying it for

acute growth hormone/ACTH/cortisol response (diagnostic-style measurement)
acute cardiac performance in coronary artery disease (intraoperative)
cardioprotection and neuroprotection (animal studies only)

Current evidence level

Early human data

Regulatory status: Not an approved medicine. Evidence strength and approval are scored separately; approval is a regulatory decision about a specific use, not a measure of how much research exists.

Human research

The published human literature on hexarelin comes almost entirely from one research group in Turin, Italy, working in the late 1990s and early 2000s. In one study, six normal young men received two or three daily subcutaneous injections of hexarelin (1.5 µg/kg) over 24-hour sampling periods; the treatment increased growth hormone secretory pulse mass without changing IGF-I, prolactin, or cortisol secretion (Maccario et al., European Journal of Endocrinology, 2002). In a second study, six normal young women received hexarelin (2.0 µg/kg IV) alongside glucagon and found the two agents had a synergistic effect on growth hormone release but a less-than-additive effect on ACTH and cortisol release (Arvat et al., European Journal of Endocrinology, 2000). A third study in six young women tested whether pretreatment with recombinant human IGF-I would blunt the ACTH, cortisol, and growth hormone responses to hexarelin and to corticotropin-releasing hormone; IGF-I reduced the growth hormone response to hexarelin but did not change its ACTH or cortisol response (Gianotti et al., Journal of Endocrinological Investigation, 2001). Separately, the same broader research group gave a single intravenous dose of hexarelin (2.0 µg/kg) to 24 men with coronary artery disease during bypass surgery and measured a real, but short-lived, intraoperative improvement in cardiac output and ejection fraction (Broglio et al., European Journal of Pharmacology, 2002). None of these four studies tested hexarelin as a treatment for any condition — each measured an acute hormonal or cardiac response in a small group over hours, not an outcome over weeks or months. No trial of hexarelin, under that name or its INN examorelin, is registered on ClinicalTrials.gov, and no human study has ever tested it for muscle growth, fat loss, recovery, or anti-aging.

Animal and preclinical research

Recent animal work on hexarelin is broader than its human research: it has been reported to protect retinal ganglion cells after nerve injury in hamsters, reduce aortic aneurysm formation and atherosclerosis in mice, improve outcomes in rat models of heart failure and diabetes, and limit lung injury in animal models. This literature is real but preclinical, spread across small, disease-specific animal models rather than one consistent line of evidence, and has not been tested in people for any of these uses.

Major findings

In six healthy young men, two or three daily subcutaneous hexarelin injections increased growth hormone secretory pulse mass over 24 hours without changing IGF-I, prolactin, or cortisol levels (Maccario et al., 2002).
In six healthy young women, hexarelin combined with glucagon produced a synergistic increase in growth hormone release but a less-than-additive effect on ACTH and cortisol (Arvat et al., 2000).
Pretreatment with recombinant human IGF-I reduced the growth hormone response to hexarelin in six healthy young women but did not change its ACTH or cortisol response (Gianotti et al., 2001).
A single intravenous dose of hexarelin given to 24 coronary artery disease patients during bypass surgery produced a measurable, short-lived improvement in cardiac output and ejection fraction (Broglio et al., 2002).
Animal studies have reported hexarelin protecting against retinal, cardiovascular, and lung injury in various rodent and hamster models, but none of this has been tested in humans.

What has not been established

Whether any of the recent animal findings — heart, brain, or blood vessel protection — translate to humans at all.
Whether repeated, long-term use has any effect beyond the acute hormone pulses measured in these small, single- or short-dose studies.
Whether hexarelin does anything for muscle mass, fat loss, or recovery in healthy adults — this has never been tested.
Why no company has taken hexarelin through a registered clinical trial in over two decades.
What is actually in an unregulated vial sold as hexarelin online.

Important limitations

All human data come from one Turin, Italy research group, working over 20 years ago, which limits independent replication.
Every human study used single doses or a few days of dosing in groups of six to 24 people — none ran longer than days.
None of the human studies tested a health outcome; all measured acute hormone levels or, in one case, intraoperative cardiac function.
No trial of hexarelin is registered on ClinicalTrials.gov, so there is no registry record to check against these published papers.
The cardiac-surgery finding was measured in the operating room under general anesthesia and IV dosing, a context with no bearing on how the compound is used today.

Regulatory status

Hexarelin is not approved as a medicine in the United States, the EU, the UK, or anywhere else. Development as a growth-hormone therapeutic was abandoned decades ago, and it is sold only as an unregulated research chemical. It is prohibited at all times in competitive sport by the World Anti-Doping Agency as a growth-hormone-releasing peptide (GHRP class, S2).

Primary research sources

Broglio F, et al., "Effects of acute hexarelin administration on cardiac performance in patients with coronary artery disease during by-pass surgery": European Journal of Pharmacology 2002; PMID 12144941, DOI 10.1016/s0014-2999(02)01934-9
Maccario M, et al., "Impact of two or three daily subcutaneous injections of hexarelin...on 24-h GH, prolactin, adrenocorticotropin and cortisol secretion in humans": European Journal of Endocrinology 2002; PMID 11888836, DOI 10.1530/eje.0.1460310
Arvat E, et al., "Interaction between glucagon and hexarelin...on somatotroph and corticotroph secretion in humans": European Journal of Endocrinology 2000; PMID 11078983, DOI 10.1530/eje.0.1430601
Gianotti L, et al., "Recombinant human IGF-I does not modify the ACTH and cortisol responses to hCRH and hexarelin...in humans": Journal of Endocrinological Investigation 2001; PMID 11263473, DOI 10.1007/BF03343815

Full evidence entry (complete data, registry records, dosing evidence)

Early human data

Small or uncontrolled human studies only

At a glance

Also known as: Examorelin, Hexarelin acetate
Class: Synthetic hexapeptide growth hormone secretagogue (GHRP family)
Derived from: A fully synthetic peptide engineered to activate the growth hormone secretagogue receptor (the same receptor targeted by the natural hormone ghrelin); not a fragment or copy of a hormone the body makes
Registered human trials: 0
…with published results: 0
Largest human trial: 24 men with coronary artery disease undergoing bypass surgery (Turin, Italy, 2002) — a single intraoperative intravenous dose used to measure acute cardiac performance, not a treatment trial
Studied for: acute growth hormone/ACTH/cortisol response (diagnostic-style measurement), acute cardiac performance in coronary artery disease, cardioprotection (animal), neuroprotection (animal)
Dosing evidence: No human dose establishedNo dose has ever been established for any therapeutic or performance use. The human studies that exist gave single or short-course injections purely to measure hormone or cardiac responses in the room, not to treat anything.
Regulatory status: Not approved as a medicine in the United States, the EU, the UK, or anywhere else. Development as a growth-hormone therapeutic was abandoned decades ago; it is sold only as an unregulated research chemical.
Anti-doping status: Prohibited at all times by the World Anti-Doping Agency, as a growth hormone-releasing peptide (GHRP class, S2)

What it is

Hexarelin is a fully synthetic chain of six amino acids, designed to trigger the same receptor that the body's natural "hunger hormone," ghrelin, acts on. Activating that receptor causes the pituitary gland to release a pulse of growth hormone. It is not a copy of anything the body produces on its own.

It is not an approved medicine anywhere, is sold only as an unregulated research chemical, and is prohibited in competitive sport at all times.

What the studies actually found

Most of what's published on hexarelin is animal work, much of it recent: it has been reported to protect retinal ganglion cells after nerve injury in hamsters, reduce aortic aneurysm formation and atherosclerosis in mice, improve outcomes in rat models of heart failure and diabetes, and limit lung injury in animal models. That literature is real but preclinical, spread across small, disease-specific animal models rather than one consistent line of evidence.

In humans, the literature is older and much narrower. A single research group in Turin, Italy, published a series of small studies in the late 1990s and early 2000s giving healthy young volunteers — usually six at a time — single or short courses of hexarelin and measuring what happened to their growth hormone, ACTH, cortisol, and prolactin over the following hours. Separately, the same group gave a single intravenous dose to 24 men with coronary artery disease during heart bypass surgery and measured an acute, short-lived improvement in cardiac output and ejection fraction — a real, measured effect, but an intraoperative one, not evidence hexarelin treats heart disease.

None of these studies tested hexarelin as a treatment for anything. They measured what a single dose or a few days of dosing did to hormone levels or heart function in the room — mechanistic and diagnostic- style research, not outcome trials.

What exists in humans

No trial of hexarelin is registered on ClinicalTrials.gov, under that name or its INN, examorelin. That is not unusual for a compound whose human studies were run in Europe in the 1990s and early 2000s, before clinical trial registries became standard — but it also means there is no registry record to check, and no company appears to have carried hexarelin through a formal drug development or approval process.

What exists instead is a handful of published journal studies, each in a handful of people, each measuring an acute hormonal or cardiovascular response rather than a treatment outcome. Anti-doping laboratories have also studied hexarelin directly, but only to build detection methods for testing athletes — confirming it is used and abused, not that it works for any marketed purpose.

No human study has ever tested hexarelin for muscle growth, fat loss, recovery, or anti-aging — the uses it is most commonly marketed for today.

What doses have been studied in humans

The published human studies used single intravenous doses (around 1.5–2.0 µg per kilogram of body weight) or short courses of subcutaneous injections over two to three days, in small groups of healthy volunteers or, in one case, surgical patients — always to measure an immediate hormonal or cardiac response, never to test a treatment over weeks or months.

No study has given hexarelin repeatedly over time to healthy adults to see what happens to muscle, fat, sleep, or aging — the reasons it is marketed today. Amounts described online for those uses do not come from any published human study. They typically trace back to animal dosing — scaled up or down to a human's body weight using a conversion formula — and that kind of conversion estimates a comparable exposure between species. It does not tell you whether the resulting amount does anything, or is safe, in a person.

What remains unknown

Whether any of the recent animal findings (heart, brain, blood vessel protection) translate to humans at all
Whether repeated, long-term use has any effect beyond the acute hormone pulses measured in these small studies
Whether it does anything for muscle mass, fat loss, or recovery in healthy adults — this has never been tested
Why no company has taken hexarelin through a registered clinical trial in over two decades
What is actually in an unregulated vial sold as "hexarelin" online

Registry and study records

Effects of acute hexarelin administration on cardiac performance in patients with coronary artery disease during by-pass surgery: PubMed · DOI: 10.1016/s0014-2999(02)01934-9 — n=24 men, single IV dose (2.0 µg/kg), intraoperative measurement only
Impact of two or three daily subcutaneous injections of hexarelin... on 24-h GH, prolactin, adrenocorticotropin and cortisol secretion in humans: PubMed · DOI: 10.1530/eje.0.1460310 — n=6 healthy young men, 2-3 days of subcutaneous dosing
Interaction between glucagon and hexarelin... on somatotroph and corticotroph secretion in humans: PubMed · DOI: 10.1530/eje.0.1430601 — n=6 healthy young women, single IV dose
Recombinant human IGF-I does not modify the ACTH and cortisol responses to hCRH and hexarelin... in humans: PubMed · DOI: 10.1007/BF03343815 — n=6 healthy young women, single IV dose

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Evidence last reviewed: September 2026. Peptide Proof reports what studies found. We do not give medical advice, dosing guidance, or treatment recommendations.