Hexarelin

Origin and structure

Hexarelin is a chain of six amino acids: His-D-2-methyl-Trp-Ala-Trp-D-Phe-Lys-NH2. It belongs to the growth-hormone-releasing peptides (GHRPs), small synthetic peptides designed to make the pituitary release growth hormone. Hexarelin is GHRP-6 with a single change: the D-tryptophan in second position carries a methyl group, chosen because 2-methyl-tryptophan is chemically more stable. Its international non-proprietary name is examorelin, which is how the anti-doping list names it, with hexarelin in brackets.

The first report, in 1994, came from Romano Deghenghi of the French company Europeptides and pharmacologists in Milan: in rats, hexarelin released about as much growth hormone as GHRP-6 when injected into a vein, and under the skin it gave a longer-lasting release and slightly more effect. Human studies followed the same year, several with the Italian drug company Mediolanum Farmaceutici. Over the next decade dozens of small studies, many from Ezio Ghigo's endocrinology group in Turin, used it to probe how growth-hormone release is controlled, as a possible diagnostic test and as a treatment for children of short stature. No company brought it to market. The clinical studies stop in 2008; since then hexarelin has been studied almost only in rats, mice and cells, above all for the heart.

How it works

Hexarelin activates the growth-hormone secretagogue receptor (GHS-R1a), the receptor through which the stomach hormone ghrelin also acts, on cells in the hypothalamus and the pituitary. Its effect adds to that of GHRH, the body's own growth-hormone-releasing hormone: a low dose of hexarelin given together with GHRH acted synergistically, releasing a large amount of growth hormone with a smaller rise in prolactin and no rise in cortisol.

It is not selective for growth hormone. In healthy men prolactin rose by up to about 180% above baseline and cortisol by about 40%, and in a direct comparison its effect on ACTH and cortisol was similar to that of CRH, the body's own stress-releasing hormone, while its prolactin effect was smaller than that of TRH. After an injection into a vein, growth hormone peaked at about 30 minutes and was back at baseline within 4 hours. Judged by the growth-hormone response, a dose under the skin worked about 77% as well as one into a vein, a nasal dose about 5% and an oral dose about 0.3%.

In the heart it has a second target. In 2002 researchers identified CD36, a scavenger receptor on heart-muscle and blood-vessel cells, as the protein hexarelin binds in rat hearts. Through CD36 it raised the pressure needed to perfuse isolated rat hearts, a sign that the coronary arteries narrowed; in hearts from mice without CD36 that effect was absent. Whether this receptor explains the short-lived rise in pumping force seen in people is not known.

Is hexarelin approved?

No. Hexarelin has never been authorised as a medicine in the EU: the EMA's databases of authorised medicines and orphan designations hold no entry for hexarelin or examorelin. The only ghrelin-receptor agonist authorised in the EU for use in people is macimorelin (Ghryvelin), an oral drug used once to test adults for growth-hormone deficiency. In the Netherlands hexarelin is not a registered medicine, so it may not be sold or promoted for use in people; it is available only as research material.

In the United States the FDA has never approved it. It also does not appear on the FDA's list of substances nominated for use by compounding pharmacies, last updated in May 2026, so it is not under evaluation for pharmacy compounding either.

In sport hexarelin is prohibited at all times, in and out of competition. The WADA Prohibited List names it, as examorelin (hexarelin), among the growth-hormone-releasing peptides in class S2.2.4; the 2026 list was published in the Dutch Tractatenblad and has applied since 1 January 2026. Anti-doping laboratories have published methods to detect hexarelin and its breakdown products in urine.

What the research shows

Since 2008 almost all published work on hexarelin has been in rats, mice and cells: protection of the heart after an infarction or a loss of blood flow, less scarring of heart tissue, and effects in models of muscle wasting, kidney injury and nerve damage. None of it has been tested in people.

Apart from a 2015 anti-doping study in which one volunteer took a nasal dose so that its breakdown products in urine could be mapped, all human data come from small studies published between 1994 and 2008, most of them measuring hormones or heart function for a few hours after a single dose. None tested a clinical outcome such as muscle, fat loss, recovery or heart failure, and none in adults lasted longer than 16 weeks. The main findings:

• First dose-response study (Imbimbo et al., 1994): double-blind and placebo-controlled, in 12 healthy men. Growth hormone rose with the dose, and the highest dose tested gave close to the maximum possible response.
• Routes (Ghigo et al., 1994): in 12 healthy young volunteers, an injection into a vein released about twice as much growth hormone as the same dose of GHRH. Doses under the skin, in the nose and by mouth also worked, the oral one only at far higher doses.
• Other hormones (Massoud et al., 1996; Arvat et al., 1997): prolactin and cortisol rose along with growth hormone in healthy adults, and growth hormone and prolactin levelled off at the same dose. In a head-to-head study in 6 young adults, hexarelin and GHRP-2 gave similar growth-hormone, prolactin, ACTH and cortisol responses.
• Sixteen weeks of use (Rahim et al., 1998 and 1999): 12 healthy older adults received injections under the skin twice daily; the published abstracts describe no placebo group. The growth-hormone response to a test dose was about a third lower after one week and about 45% lower at 16 weeks, and was back to its starting level 4 weeks after the last dose. IGF-1, fat mass, lean mass and bone density did not change, the prolactin response and 24-hour urinary cortisol stayed the same, and the cortisol response to each dose became smaller.
• Children of short stature (Laron et al., 1995; Klinger et al., 1996): in 8 prepubertal children given hexarelin as a nasal spray for up to 8 months, IGF-1 rose from 10.4 to 14.1 nmol/l and growth speed from 5.3 to 8.3 cm a year. In 7 children followed for 6 to 10 months, the growth-hormone response to a test dose halved within a week, yet growth still sped up. Neither study had a control group.
• Heart (Bisi et al., 1999; Imazio et al., 2002; Broglio et al., 2002): a single injection into a vein raised the left-ventricular ejection fraction, the share of blood the heart pumps out with each beat, in 7 healthy men (from 64% to 71%, for up to an hour), in 7 men with growth-hormone deficiency whose growth hormone barely rose, and in 5 patients with ischaemic cardiomyopathy, but not in 8 with dilated cardiomyopathy. In 24 men undergoing bypass surgery, divided between hexarelin, GHRH, growth hormone and placebo, only hexarelin raised ejection fraction and cardiac output, for up to 90 minutes.
• Sleep (Frieboes et al., 2004): in a placebo-controlled study in 7 young volunteers, four hourly doses between 22:00 and 01:00 reduced deep sleep and raised growth hormone, prolactin, ACTH and cortisol during the night.

Desensitisation and side effects

The growth-hormone response to hexarelin wears off with repeated use, a process called desensitisation. In the 16-week study in older adults it was a third lower after one week and about 45% lower at the end, and it recovered fully within 4 weeks of stopping; in children on the nasal spray it halved within a week and had only partly recovered 3 months after stopping. IGF-1 told a different story in the two groups: unchanged in the adults, higher in the children.

Side effects were rarely reported, but the studies were small and short. What recurs is that hexarelin is not selective: every dose raises prolactin, ACTH and cortisol along with growth hormone. In the 16-week study this did not build up: the cortisol response to each dose shrank, and the prolactin response and 24-hour urinary cortisol did not change. Late-evening doses reduced deep sleep. There are no data on use beyond 16 weeks in adults, on cancer risk from raised growth hormone, or on pregnancy.

Frequently asked questions

Is hexarelin legal in the Netherlands?

It is not a registered medicine in the Netherlands and has never been authorised by the EMA, so it may not be sold, advertised or supplied for use in people. Buying and selling it as research material is a different status. For athletes under anti-doping rules it is prohibited however it was obtained.

Is hexarelin banned in sport?

Yes, at all times, in and out of competition. The WADA Prohibited List names it as examorelin (hexarelin) in class S2.2.4, growth-hormone-releasing factors, and the Dutch anti-doping rules apply the same list. Laboratories can detect hexarelin and its breakdown products in urine.

Does hexarelin stop working with repeated use?

Partly. In 12 healthy older adults on twice-daily injections, the growth-hormone response to a test dose was about a third lower after one week and about 45% lower after 16 weeks, and it was back to normal 4 weeks after stopping. In children on a nasal spray it halved within a week. In the adults, IGF-1 did not change over the whole study.

What is the difference between hexarelin and GHRP-6?

Hexarelin is GHRP-6 with a methyl group added to its second amino acid, a change made for chemical stability. In rats the two released about the same amount of growth hormone after an injection into a vein, and hexarelin was slightly more effective under the skin. In people, a head-to-head study compared it with GHRP-2 and found similar growth-hormone, prolactin, ACTH and cortisol responses.

Is hexarelin good for the heart?

That is not established. A single injection briefly raised the heart's pumping force in small groups of healthy men, people with growth-hormone deficiency, patients with ischaemic heart disease and men during bypass surgery, apparently not through growth hormone. No study has given repeated doses to heart patients or measured symptoms, hospital admissions or survival. The protective effects after a heart attack come from rats and mice, and in isolated rat hearts hexarelin also narrowed the coronary arteries.

Is hexarelin safe?

For short use in clinical studies few side effects were reported, but every dose raised prolactin, ACTH and cortisol along with growth hormone, and late-evening doses reduced deep sleep. The longest adult study lasted 16 weeks, and there are no data on longer use, cancer risk or pregnancy, so its longer-term safety is unknown.

Storage and handling

Store according to product-label instructions and batch handling notes. Lyophilized research peptides are commonly kept dry, protected from light, and handled with clean laboratory technique.

References

Checked against these sources on 28 October 2026.