Hexarelin is a six-amino-acid peptide that differs from GHRP-6 by a single methyl group on the second residue, a change made by Romano Deghenghi's group in Italy in the early 1990s to make the molecule more stable. The 1994 paper that introduced it showed it releasing growth hormone in both infant and adult rats. Like the rest of its family it acts on the ghrelin receptor in the pituitary and hypothalamus, not on the receptor for growth hormone releasing hormone. It was studied intensively in Italian clinics through the 1990s and then largely set aside; it is not an approved drug in any country.

HexarelinWhat the studies show

Q: What kind of evidence exists for hexarelin?

Small human studies. Rat pharmacology and small human hormone studies from the 1990s, including one 16-week dosing study showing the growth hormone response fades; good evidence of what it does acutely, no evidence of any outcome, and no approval anywhere.

GHRP-6 with one methyl group added, active by mouth and nose as well as by injection, and the GHRP whose growth hormone response was shown to fade by 16 weeks.

5 min read · Small human studies · Updated November 2026

In short

Name: hexarelin
Evidence: Small human studies
Bottom line: Rat pharmacology and small human hormone studies from the 1990s, including one 16-week dosing study showing the growth hormone response fades; good evidence of what it does acutely, no evidence of any outcome, and no approval anywhere.

Before you read this

This guide explains what published studies found. That is all it is.

It is not medical advice and it is not instructions for using anything. Where a dose appears, we are reporting what a named study gave the people or animals in it — a fact about the study, not an instruction to you.

The compounds here are not approved by the FDA for use in people and are sold for laboratory research only. A study tells you what happened to the subjects in it; it does not tell you what would happen to you. Talk to a doctor first.

What it is

Hexarelin is a six-amino-acid peptide that differs from GHRP-6 by a single methyl group on the second residue, a change made by Romano Deghenghi's group in Italy in the early 1990s to make the molecule more stable. The 1994 paper that introduced it showed it releasing growth hormone in both infant and adult rats ¹. Like the rest of its family it acts on the ghrelin receptor in the pituitary and hypothalamus, not on the receptor for growth hormone releasing hormone. It was studied intensively in Italian clinics through the 1990s and then largely set aside; it is not an approved drug in any country.

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In people, by four routes

The first human study, published in 1994, gave hexarelin to healthy volunteers intravenously, under the skin, into the nose and by mouth, and measured growth hormone after each. It released growth hormone by all four routes, with the oral route needing a far larger dose than the other three ². That made hexarelin, for a while, the most practical GHRP to study, and most of the clinical literature on this class from the mid-1990s uses it. Most of the Italian studies that followed gave it by vein and measured the growth hormone peak over the following hours, which is where the comparative figures between hexarelin, GHRP-6 and GHRH in the review literature come from.

The response is not confined to growth hormone. A 1997 comparison of hexarelin and GHRP-2 in healthy adults found that both raised prolactin, ACTH and cortisol in addition to growth hormone, though less than the hormones that specifically release each of those ³. This is the pattern the later peptide ipamorelin was designed to avoid.

What happens over weeks

The most useful hexarelin study for anyone thinking about repeated use was done in Manchester and published in 1998. Healthy adults were given hexarelin under the skin twice a day for 16 weeks, and the growth hormone response to a test dose was measured along the way. It shrank: after weeks of dosing, the same injection released markedly less growth hormone than it had at the start, and the response had recovered when the volunteers were retested after a period off the peptide ⁴. Partial desensitisation of this kind is the clearest evidence in the whole GHRP literature that the acute single-dose studies overstate what a daily schedule delivers.

The heart finding

Hexarelin has a second story. Researchers in Montreal found that it binds CD36, a receptor on heart and blood-vessel cells that has nothing to do with growth hormone, and that this binding accounted for effects on coronary blood flow in isolated rat hearts that persisted in animals with no growth hormone response at all ⁵. A small 2002 study gave hexarelin to patients with coronary artery disease during bypass surgery and reported acute changes in measures of heart pumping ⁶. These are mechanism and pilot findings in a handful of animals and patients, not trials of any heart outcome.

What is not known

Hexarelin has no placebo-controlled trial for body composition, strength, recovery or ageing in people, and the one longer study found its main effect wearing off. The cardiac work stopped at the mechanism stage. What exists is a well-documented acute hormone response in people, a well-documented fade with repeated dosing, and nothing about outcomes. Even the 16-week study measured hormones rather than muscle or fat, so the fade itself is a fact about a blood test.

What these studies are, and aren't

Small human studies. Rat pharmacology and small human hormone studies from the 1990s, including one 16-week dosing study showing the growth hormone response fades; good evidence of what it does acutely, no evidence of any outcome, and no approval anywhere.