GHRP-6

A synthetic six-amino-acid peptide, made in 1984 and the first of the compounds called growth-hormone-releasing peptides. Two of its six building blocks — the tryptophan in position 2 and the phenylalanine in position 5 — are mirror-image forms, and the chain ends in an amide cap rather than a normal end, so it cannot be written correctly in the standard one-letter code; we mark it unknown rather than print a misleading string. It has never been approved as a medicine anywhere. It is sold online as a freeze-dried powder labelled for research use only, and it is still in development in Cuba as CIGB-500, a candidate treatment for heart attack.

Sold as

Injection under the skin or into a vein. Published studies have also given it by mouth, into the nose and under the tongue; whether swallowing it works is contested.

Legal status in the EU

Not approved as a medicine in the EU, the US or anywhere else. The US FDA placed it on its list of bulk drug substances that may present significant safety risks on 29 September 2023, citing the risk that the immune system reacts to clumps and impurities in the peptide, a potential effect on cortisol, and a rise in blood sugar from reduced insulin sensitivity. In Sweden, the doping law (1991:1969) covers in its own words "chemical substances that increase the production or release of ... growth hormone", which is a description of what GHRP-6 does, and makes importing, possessing or using such substances outside medical or scientific purposes a criminal offence. Named by name on the WADA Prohibited List 2026, section S2.2.4, under GH-releasing peptides — banned at all times, in and out of competition.

It switches on the ghrelin receptor in the pituitary gland — the same switch the hunger hormone ghrelin uses — and the gland releases a burst of growth hormone. That is a different route from the natural hormone GHRH, which is why giving both together produces far more growth hormone than either alone. It is not selective: it also drives the chain that ends in the stress hormone cortisol, and raises the milk hormone prolactin. In animals it acts on the appetite centres of the brain directly, making sated rats eat without changing their growth hormone at all.

Part of the bodyWhat happensHow it is knownKind of evidence

The pituitary gland, at the base of the brain

GHRP-6 latches onto the same switch on the pituitary gland that the hunger hormone ghrelin uses, and the gland releases a burst of growth hormone. The burst is fast and short: growth hormone starts climbing within a few minutes, peaks at around 15 to 30 minutes, and is back to normal within about two hours. How big the burst is depends closely on the amount given. In 18 healthy men, a small injection lifted peak growth hormone from about 1 to about 8 nanograms per millilitre, and a ten-times-larger one lifted it to about 69. It works through a different route from the older hormone GHRH, which is why giving both together produces far more growth hormone than either alone.

Measured in 18 healthy men in the first published human study, and repeated since in hundreds of adults and children across more than thirty published studies in Italy, Spain, Serbia, Germany, the United States and Cuba. The largest single dataset is 125 healthy adults and 125 adults with pituitary disease, all given GHRP-6 together with GHRH.

Measured in people

Source [01]Source [02]Source [14]

The stress hormones, cortisol and ACTH

GHRP-6 does not only release growth hormone. It also switches on the chain that ends in cortisol, the body's main stress hormone: the brain releases ACTH, and ACTH tells the adrenal glands to release cortisol. In 18 healthy men this happened only at the largest amount tested, where cortisol and the milk hormone prolactin both roughly doubled. Overnight, after four small injections, cortisol in the first half of the night was more than twice as high as after a dummy injection. This is the opposite of what GHRH does, which if anything dampens cortisol overnight. The effect is reliable enough that doctors have used GHRP-6 as a test of whether someone's adrenal glands work at all.

Measured in 18 healthy men after a single injection, in healthy men across a night in a sleep laboratory against a dummy injection, and in 49 patients with pituitary or adrenal disease plus 20 healthy controls in a German hospital study.

Measured in people

Source [01]Source [03]Source [15]

Heart rate, sweating and drowsiness

In the one study that gave healthy men large amounts and watched them in an intensive care unit for three days, the commonest things that happened were sweating and a slowed heart rate. Both got more likely as the amount went up: at the largest amount, all three men had a slowed heart rate, all three sweated and all three became drowsy. The slowing lasted between about an hour and three hours and settled by itself. Nobody needed treatment for any of it. A 28-day study in dogs found the same slowed heart rate at every amount given, and it went away after treatment stopped.

Measured in 18 healthy Cuban men aged 22 to 35, three men at each of six escalating amounts, given a single injection into a vein and watched in hospital for 72 hours and then followed for a further 7 days. There was no dummy-injection group, so the ordinary rate of sweating or heart-rate change in men lying in an intensive care unit is unknown.

One small study

Source [04]Source [16]

Sleep

Four small injections given across an evening changed the shape of a night's sleep, but not in the direction people hope for. Light sleep — stage 2 — increased by about 25 minutes. Deep slow-wave sleep, the kind that is supposed to matter for recovery, did not change at all. A follow-up study by the same group found the effect depends entirely on how the compound gets in: taken as capsules by mouth it did nothing to sleep hormones, sprayed into the nose it raised growth hormone across the night, and under the tongue it did almost nothing.

Measured in healthy young men in a sleep laboratory, each man compared with himself on a dummy-injection night. The published abstract of the first study does not state how many men took part.

One small study

Source [15]Source [17]

Appetite, in the brain

This is what GHRP-6 is best known for and it has only been seen in animals. Injected directly into the fluid space of a rat's brain, it made sated rats start eating, and the bigger the amount the more of them ate — while growth hormone in their blood did not change at all, which means the hunger is a separate effect and not a knock-on from the growth hormone. Later work showed it switches on the same brain regions that the hunger hormone ghrelin switches on. In diabetic rats, GHRP-6 given daily for eight weeks alongside insulin produced more weight gain and more belly fat than insulin alone; given without insulin it did nothing. No published human study of GHRP-6 has ever asked a person whether they felt hungry, or measured how much they ate.

Seen in rats given it into the brain, in rats and mice mapped for brain activity, and in diabetic rats treated daily for eight weeks. Never measured in a person, in any study, at any amount, by any route.

Only seen in animals

Source [18]Source [19]Source [20]

Muscle and body fat

Only measured in animals, and only as body weight. In the 1984 paper that first described the compound, young rats injected once or twice a day for 9 or 25 days gained more weight than untreated rats, and their pituitary glands still responded at the end. That is a weight on a scale, not muscle: nothing was separated into lean tissue and fat. No published study has ever weighed a person's muscle or fat, tested anyone's strength, or measured anyone's body composition while giving them GHRP-6.

Seen in immature rats injected under the skin once or twice daily for 9 or 25 days against untreated rats. Never measured in a person.

Only seen in animals

Source [13]Source [21]

Wounds and scars

Only seen in animals, and only when smeared on rather than injected. A Cuban laboratory put GHRP-6 in a jelly on full-thickness wounds in rats twice a day for four days and the wounds closed faster than wounds treated with the jelly alone. In rabbit ears, which are used as a model for thick raised scars, daily treatment for 30 days prevented that kind of scar in about 9 out of 10 treated wounds, while about 9 out of 10 untreated wounds developed one.

Seen in 10 rats with 20 wounds, and in rabbits across four separate experiments covering 84 treated and 80 untreated wounds. Never tested on a human wound in a published study.

Only seen in animals

Source [22]

The one job GHRP-6 was formally tested at against an established standard, it did worse than the standard: Alaioubi and colleagues (Horm Metab Res 2010) tested it as a way of diagnosing adrenal failure in 49 patients and 20 controls, and reported that it activated the system reliably but had limited accuracy compared with the insulin tolerance test. Apart from that, the human record is thirty-five years of acute hormone-response experiments. Bowers and colleagues (J Clin Endocrinol Metab 1990) gave it to 18 healthy men and peak growth hormone rose from 1.2 nanograms per millilitre on a dummy injection to 68.7 at the largest amount; the same injection roughly doubled cortisol and prolactin. Popovic and colleagues (Lancet 2000) used it with GHRH as a diagnostic test in 125 pituitary patients and 125 controls. A Cuban phase 1 study (18 healthy men, single injection, six escalating amounts, 2014) is the only published safety study and had no control group. No trial has ever tested GHRP-6 as a treatment for anything: a search of clinicaltrials.gov on 2026-08-03 returned zero registered studies under any spelling. Nothing has been published on muscle, body fat, strength, healing or appetite in a person. The only study to give repeated doses over more than one day — 300 micrograms per kilogram twice daily for 4 days in 7 elderly women — found the growth signal IGF-1 unchanged, from 77.1 to 84.1 micrograms per litre.

Everything happens fast and is over quickly. After an injection into a vein, growth hormone begins rising within minutes, peaks at around 15 to 30 minutes, and is usually back to normal within about two hours. The compound itself leaves the bloodstream with a half-life — the time for half of it to go — of about 7.6 minutes, and is cleared from the body with a half-life of about 2.5 hours, though it is still measurable 12 hours later. The slowed heart rate seen in the Cuban study came on inside the first half hour and lasted between 55 minutes and 3 hours. Beyond that nothing is known: the only published measurement over more than one day is four days of capsules in seven women, and it found that IGF-1, the growth signal that growth hormone works through, had not moved.

What was measuredWhat happenedIn whomHow it is known

Growth hormone in the blood after a single injection

Peak growth hormone was 1.2 nanograms per millilitre after a dummy injection, and 7.6, 16.5 and 68.7 after 0.1, 0.3 and 1.0 micrograms of GHRP-6 per kilogram of body weight. Every step up in the amount produced a step up in the response. Giving GHRP-6 and the hormone GHRH together produced more growth hormone than adding the two effects together would predict.

18 healthy men, each given a dummy injection and several amounts of GHRP-6 into a vein on separate occasions.

Measured in people

Source [01]

Telling apart adults who make growth hormone from adults who do not

Average peak growth hormone after GHRH plus GHRP-6 was 59.2 nanograms per millilitre in healthy people and 4.1 in people with pituitary disease. The old standard test, which works by deliberately dropping someone's blood sugar with insulin, gave 14.3 and 0.5 in the same people. The gap between healthy and ill was wider with the peptide test, and unlike the old test it was not thrown off by age, sex or body fat. The authors report that the peptide test caused no side effects.

125 adults with pituitary disease and 125 healthy adults, across several hospitals. All were given GHRH and GHRP-6 into a vein; the patients and 27 of the healthy people also had the old insulin test.

Measured in people

Source [02]

Telling apart people whose adrenal glands work from people whose adrenal glands have failed

This is the one job GHRP-6 was formally tested at against an established standard, and it did worse than the standard. Peak cortisol after GHRP-6 was 227 nanomoles per litre in the people whose adrenal glands had failed and 395 in those whose had not — an overlap wide enough that the best possible cut-off still got about 3 in 10 people wrong. The authors' conclusion was that GHRP-6 activates the system reliably but has limited accuracy compared with the insulin test. They also record that it caused no detectable side effects.

49 patients with suspected failure of the brain-to-adrenal-gland chain and 20 healthy controls. Patients had both the GHRP-6 test and the old insulin test.

Measured in people

Source [03]

Whether swallowing it works

The two published attempts disagree. Bellone and colleagues gave 300 micrograms per kilogram of body weight by mouth to short but otherwise healthy children and growth hormone rose from 1.1 to a peak of 18.8 nanograms per millilitre at 60 minutes — as large as an injection of GHRH into a vein. Frieboes and colleagues gave the same amount by mouth in enteric-coated capsules to healthy adult men in the evening and growth hormone, ACTH and cortisol all stayed exactly where they were. Neither result has been repeated.

13 children aged 6 to 10, of whom the first 7 received oral GHRP-6; and healthy young adult men in a sleep laboratory, each compared with himself on a dummy night.

Studies in people disagree

Source [17]Source [23]

Hormones and sleep across a whole night

Growth hormone across the early night was 15.4 nanograms per millilitre after GHRP-6 against 5.5 after a dummy injection. ACTH was 21.0 against 16.6 picograms per millilitre, and cortisol was 56.0 against 25.2 nanograms per millilitre — so the stress hormone more than doubled. Light stage-2 sleep rose from 245 to 270 minutes. Deep slow-wave sleep did not change.

Healthy young men, each compared with himself on a dummy-injection night, given four injections of 50 micrograms into a vein across the evening. The abstract does not state how many men took part.

One small study

Source [15]

IGF-1, the growth signal that growth hormone actually works through

It barely moved. After four days of capsules taken twice a day, IGF-1 went from 77.1 to 84.1 micrograms per litre, a change the authors report as not statistically significant. The growth hormone burst itself was still there on day four and if anything a little larger, so the pituitary gland had not stopped responding — the downstream signal simply had not caught up. This is the only published measurement of what more than one dose of GHRP-6 does to IGF-1 in a person, and there was no dummy-treatment group.

7 healthy women aged 65 to 82, each compared with herself before and after four days of treatment.

One small study

Source [06]

How long the compound itself stays in the blood

It clears in two stages. It leaves the bloodstream and spreads into the tissues with a half-life — the time for half of it to go — of about 7.6 minutes, and is then removed from the body with a half-life of about 2.5 hours. It was still measurable 12 hours after the injection in every man. Four of the nine men showed unexplained spikes in the level while it was clearing, which the authors report without accounting for.

9 healthy men, given a single injection into a vein at one of three amounts: 100, 200 or 400 micrograms per kilogram of body weight.

One small study

Source [05]

Body weight, in young rats given it daily

Rats injected once or twice a day for 9 or 25 days gained more weight than untreated rats, and their pituitary glands still responded fully at the end of the experiment. Nothing was measured except weight — the gain was never separated into muscle and fat.

Immature rats, treated for 9 or 25 days against untreated rats.

Only seen in animals

Source [21]

The only published safety study gave single injections to 18 healthy men in hospital and had no comparison group: 9 sweated, 8 had a slowed heart rate lasting between 55 minutes and 3 hours, and all 3 men at the largest amount became drowsy. Nothing was serious. The same slowed heart rate appeared at every dose in a 28-day dog study. Unlike the newer peptides sold beside it, GHRP-6 raises the stress hormone cortisol and the milk hormone prolactin — both roughly doubled at the largest single amount in healthy men. The US regulator names three concerns: that the immune system reacts to clumps and impurities in the peptide, a potential effect on cortisol, and a rise in blood sugar from reduced insulin sensitivity. Nothing is known beyond ten days, which is the longest anyone has been followed in a published study. Powders seized by Danish and German customs turned out to contain a glycine-extended version of GHRP-6 rather than GHRP-6 itself, and nobody has studied what that does in a person.

EffectWhat it feels likeHow often

A slowed heart rate

It came on within the first half hour and lasted between about 55 minutes and 3 hours. The authors looked for a link between how much was given, how high the level in the blood went and how far the heart rate dropped, and found no statistically significant correlation — only a trend in that direction, which they report as a description rather than a result. Nobody needed treatment and it resolved on its own in every case. The same slowing turned up in dogs given daily injections for 28 days, at every amount tested, and it went away after treatment stopped.

8 of the 18 men in the Cuban safety study, and all 3 of the men given the largest amount. There was no dummy-injection group to compare against.

Source [04]Source [16]

Sweating

Short-lived — a few minutes at the small amounts, up to about 45 minutes at the largest. One episode was graded moderate; every other side effect in the study was graded mild.

9 of the 18 men in the Cuban safety study, at every amount from the second-lowest upwards. No dummy-injection group.

Source [04]

Drowsiness

Only seen at the top of the dose range. It fits the sleep laboratory finding that GHRP-6 pushes up light sleep.

3 of the 18 men — all three of the men given the largest amount, 400 micrograms per kilogram of body weight, and nobody below that.

Source [04]

A rise in the stress hormone cortisol and in prolactin

Prolactin is the hormone that drives milk production; a lasting rise can affect periods, sex drive and erections. Cortisol is the body's main stress hormone. Neither belongs in a compound taken for muscle, and this is the main thing that separates GHRP-6 from the newer peptides sold beside it. Nobody has measured what either hormone does over weeks of repeated use, because nobody has run that study.

Roughly doubled at the largest single amount in the first human study, and not at smaller amounts. Overnight, after four small injections, cortisol in the first half of the night was more than double the dummy-injection night.

Source [01]Source [13]Source [15]

Shortness of breath, a fast heart rate, a slight temperature

Single events in a study of 18 people, which is exactly the size at which one event cannot be told apart from chance. All three resolved without treatment. The study's own abstract reports 23 side-effect events in total and its results table adds up to 25; both figures are printed here because both are in the same paper.

One man each, out of the 18 in the Cuban safety study.

Source [04]

Higher blood sugar and worse insulin sensitivity

When the US regulator listed GHRP-6 in September 2023 among substances that may present significant safety risks in compounded medicines, it gave three reasons: a risk that the immune system reacts to the peptide clumping together or to related impurities in it, a potential effect on cortisol, and a rise in blood sugar caused by the body responding less well to insulin. Growth hormone kept high does this, and the longest anyone has been followed after taking GHRP-6 in a published study is ten days.

Not measured over any meaningful period. The US regulator names it as a known concern; no human study has run long enough to see it.

Source [07]

Anything that takes more than ten days to appear

Almost every human study of GHRP-6 gave one dose and measured blood for two hours. The two exceptions are four days of capsules in seven elderly women and one night in a sleep laboratory. Nothing is known about repeated injections over weeks or months in a person: not what happens to blood sugar, not what happens to the pituitary gland, not whether the immune system starts making antibodies against it, and not whether pushing growth hormone up for months carries the risks that approved growth hormone medicines carry warnings about.

Not measured. The longest anyone has been watched in a published human study is 10 days, and that was after a single injection.

Source [04]Source [07]Source [13]

These are the amounts the studies below gave their participants, and they are here as facts about those studies. They are not a recommendation, not a starting point and not a range to pick from. What a person should take, if anything, is a question for a doctor who knows them.

Bowers and colleagues 1990, the first human study — what a single injection does to growth hormone in 18 healthy men, against a dummy injection

A single injection into a vein: 0.1, 0.3 or 1.0 micrograms per kilogram of body weight, given alone and together with 1.0 micrograms per kilogram of the hormone GHRH.

A single injection, with blood taken over the following hours.

Source [01]

Popovic and colleagues 2000 — the diagnostic test, in 125 adults with pituitary disease and 125 healthy adults

A single injection into a vein of 1 microgram per kilogram of body weight, given together with 1 microgram per kilogram of GHRH.

One injection, with blood taken over 120 minutes.

Source [02]

The Cuban phase 1 safety study 2014 — the highest amounts ever given to a person in a published study, in 18 healthy men aged 22 to 35, three men per step

A single injection into a vein over three minutes, at six escalating amounts in micrograms per kilogram of body weight: 1, 10, 50, 100, 200 and 400.

A single injection, followed by 72 hours in hospital and a further 7 days of follow-up — 10 days in total.

Source [04]Source [05]

Ghigo and colleagues 1994 — the only published study that gave a person more than one dose over more than one day, in 7 healthy women aged 65 to 82

300 micrograms per kilogram of body weight by mouth, twice a day.

4 days.

Source [06]

Bellone and colleagues 1995 — swallowed rather than injected, in 13 short but otherwise healthy children aged 6 to 10

300 micrograms per kilogram of body weight by mouth, compared against 1 microgram per kilogram of GHRH into a vein.

A single dose.

Source [23]

Frieboes and colleagues 1995 and 1999 — the sleep laboratory studies in healthy young men, against dummy nights

Four injections of 50 micrograms into a vein across the evening in the first study. In the second study, 300 micrograms per kilogram of body weight in enteric-coated capsules by mouth, or 30 micrograms per kilogram into the nose, or 30 micrograms per kilogram under the tongue.

One night per condition.

Source [15]Source [17]

What people report

• Whether it makes anyone hungry — the effect it is most famous for has never been measured in a person.
• Whether it builds any muscle or adds any strength in a person: never measured, in any study, at any amount.
• Whether it changes body fat in a person: never measured, in any study.
• Whether it improves sleep quality: the one sleep study found more light sleep and no change at all in deep sleep.
• Whether it helps any injury or wound heal in a person — the healing work is rats and rabbits, treated by smearing it on rather than injecting it.
• What happens after ten days, which is the longest anyone has been followed in a published human study.
• What repeated injections do to blood sugar and insulin, which is the risk the US regulator named when it listed the substance in 2023.
• What repeated use does to the stress hormone cortisol and to prolactin, both of which rise after a single dose.
• Whether the pituitary gland stops responding with continued use: four days of capsules did not blunt it, and that is the whole of what is known.
• Whether the immune system makes antibodies against it over time — nobody has looked, in any study.
• Whether taking it by mouth works at all: one study in children got a large growth hormone rise and one in adult men got nothing, and neither has been repeated.
• Why swallowing it appeared to work in children but not in adults — the two studies used different formulations and different times of day, and no one has tested which explanation is right.
• Whether it does anything for people who actually have a growth hormone deficiency: it has been used to diagnose them, never to treat them.
• What the glycine-extended version found in seized powders does in a person: it has never been given to one in a published study.
• Whether women respond differently: the two safety studies enrolled men only, and the one repeat-dose study enrolled seven women and nobody else.
• What it does over years, at the amounts and cycle lengths that circulate online — nobody has given a person GHRP-6 repeatedly for more than four days in a published study.
• How many people have been harmed by it: the US side-effect database returns no reports for GHRP-6 under any spelling, which measures reporting habits rather than safety.

Does GHRP-6 work?

It depends entirely on what you mean by work. At releasing growth hormone, yes, reliably and in almost everyone: in the first human study a single injection lifted peak growth hormone from about 1 to about 69 nanograms per millilitre at the largest amount, and dozens of later studies found the same. At anything a person would actually notice — more muscle, less fat, better sleep, faster healing, more appetite — nobody knows, because in thirty-five years no published study has measured any of those things in a person taking GHRP-6.

Source [01]Source [13]

Is GHRP-6 legal?

It is not an approved medicine anywhere, so there is no legal way to be prescribed it as a treatment. In the United States the regulator listed it in September 2023 among bulk substances that may present significant safety risks when used in compounded medicines, citing an effect on cortisol and a rise in blood sugar. In Sweden the doping law of 1991 covers, in so many words, chemical substances that increase the production or release of growth hormone — which is the definition of what GHRP-6 does — and makes importing, possessing or using them outside medical or scientific purposes a criminal offence.

Source [07]Source [09]

What are the side effects of GHRP-6?

In the only study that gave healthy men large amounts and watched them in hospital, 9 of 18 men sweated, 8 of 18 had a slowed heart rate lasting up to three hours, and the three men given the largest amount all became drowsy. There was one case each of shortness of breath, a fast heart rate and a slight temperature. Nothing was serious and everything resolved by itself, but there was no comparison group, so the ordinary rate of these things in men lying in an intensive care unit is unknown. GHRP-6 also pushes up the stress hormone cortisol and the milk hormone prolactin, which the newer peptides sold beside it mostly do not.

Source [01]Source [04]Source [15]

GHRP-6 vs ipamorelin — what is the difference?

They pull the same lever, but GHRP-6 pulls another one as well. Both switch on the ghrelin receptor in the pituitary gland to release growth hormone, and in pigs they did it about equally well. The difference is what else happens: in that same comparison, GHRP-6 raised ACTH and the stress hormone cortisol and ipamorelin did not, at any amount tested. In healthy men, GHRP-6 roughly doubled both cortisol and the milk hormone prolactin at the largest amount given. Neither compound is approved anywhere; ipamorelin at least reached a randomised trial as a treatment — in patients recovering from bowel surgery, where it did not beat a dummy drip — while GHRP-6 has never had a treatment trial at all.

Source [01]Source [13]Source [24]

Does GHRP-6 make you hungry?

In rats, yes, and unmistakably — injected straight into the brain it made already-fed rats start eating, with more of them eating the more they were given. In people, nobody knows, because not one published human study of GHRP-6 has asked a participant whether they were hungry or measured what they ate. The hunger claim is the single most repeated thing about this compound online and it is also the single clearest gap in its human record.

Source [18]Source [19]

Does GHRP-6 build muscle?

No published study has ever weighed a person's muscle while giving them GHRP-6, so there is no evidence either way. The closest thing is the 1984 paper that first described it, where young rats injected daily for up to 25 days gained more body weight than untreated rats — a number on a scale that was never separated into muscle and fat. Growth hormone works on the body through a second signal called IGF-1, and the only study that measured IGF-1 after more than one dose of GHRP-6 found it had not significantly moved after four days.

Source [06]Source [21]

Can you buy GHRP-6?

It is sold online as a freeze-dried powder labelled for research use only, which is a label rather than a licence — there is no approved medicine containing it anywhere in the world. What arrives is a separate question from what is ordered: doping laboratories analysing powders seized by Danish and German customs found not GHRP-6 but a modified version carrying an extra amino acid on the front, and nobody has studied what that version does in a person. This register does not link to sellers or list prices.

Source [07]Source [12]Source [25]

Is GHRP-6 banned in sport, and can it be tested for?

Yes to both. The 2026 prohibited list names GHRP-6 by name under growth hormone releasing peptides in section S2.2.4, which is banned at all times, in and out of competition. It is also testable: a laboratory method for finding GHRP-6 and its relatives in urine was published in 2011, and a doping laboratory in Salt Lake City published a report on detecting GHRP-6 in urine samples from athletes in 2015.

Source [08]Source [26]Source [27]

Why is there no sequence shown for GHRP-6?

Because writing one would be a lie. GHRP-6 is six amino acids long, but two of them — the tryptophan in position 2 and the phenylalanine in position 5 — are mirror-image versions of the natural building blocks, and the chain ends in an amide cap rather than a normal end. The standard one-letter code has no way to say any of that, so the string HWAWFK would describe a different molecule that would not do what GHRP-6 does. The register prints nothing rather than something that looks right.

Source [10]Source [21]

1. [01]Bowers CY et al. Growth hormone (GH)-releasing peptide stimulates GH release in normal men and acts synergistically with GH-releasing hormone. J Clin Endocrinol Metab 1990;70(4):975-82 (18 healthy men; peak GH 1.2 / 7.6 / 16.5 / 68.7 µg/L) (1990)
2. [02]Popovic V et al. GH-releasing hormone and GH-releasing peptide-6 for diagnostic testing in GH-deficient adults. Lancet 2000;356(9236):1137-42 (125 patients, 125 controls) (2000)
3. [03]Alaioubi B et al. Diagnosis of adrenal insufficiency using the GHRP-6 test: comparison with the insulin tolerance test. Horm Metab Res 2010;42(3):198-203 (49 patients, 20 controls; limited accuracy vs ITT) (2010)
4. [04]Selman-Housein Bernal KH et al. Clinical safety of Growth Hormone-Releasing Peptide 6 (GHRP-6) in healthy volunteers. Invest Medicoquir 2014;6(1):81-91 (phase 1, 18 men, 1–400 µg/kg IV, no control group; full text PDF) (2014)
5. [05]Cabrales A et al. Pharmacokinetic study of Growth Hormone-Releasing Peptide 6 (GHRP-6) in nine male healthy volunteers. Eur J Pharm Sci 2013;48(1-2):40-6 (distribution half-life 7.6 min, elimination 2.5 h) (2013)
6. [06]Ghigo E et al. GH-releasing activity of GHRP-6 is maintained after short-term oral pretreatment with the hexapeptide in normal aging. Eur J Endocrinol 1994;131(5):499-503 (7 women, 4 days, IGF-I 77.1→84.1 µg/L, not significant) (1994)
7. [07]FDA: Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks — GHRP-6 entry (503B, added 29 September 2023) (2023)
8. [08]WADA: World Anti-Doping Code International Standard – Prohibited List 2026, section S2.2.4, GH-releasing peptides (GHRP-6 named by name; in force 1 January 2026) (2026)
9. [09]Lag (1991:1969) om förbud mot vissa dopningsmedel, 1 § — "kemiska substanser som ökar produktion eller frigörelse av testosteron och dess derivat eller av tillväxthormon" (in Swedish) (1991)
10. [10]PubChem CID 9919153 (CAS 87616-84-0), GHRP-6 — C46H56N12O6, 873.0 g/mol, IUPAC name carrying 2R at the position-2 tryptophan and 2R at the position-5 phenylalanine, plus a C-terminal amide
11. [11]ClinicalTrials.gov API v2, exact-phrase query for "growth hormone releasing peptide 6" — totalCount 0. The same query for GHRP-6, GHRP6, CIGB-500 and as an intervention also returns 0 (checked 2026-08-03). Searched unquoted the API word-matches and returns 486 unrelated studies.
12. [12]Gajda PM et al. Glycine-modified growth hormone secretagogues identified in seized doping material. Drug Test Anal 2019;11(2):350-4 (2019)
13. [13]Dominikowski A et al. The emerging landscape of performance-enhancing peptides modulating the GH-IGF1 axis. Front Endocrinol 2026;17:1822475 (free full text) (2026)
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