MK-677 (ibutamoren)

Not a peptide. MK-677 is a small molecule you swallow — PubChem gives the formula C27H36N4O5S and a structure built around a spiro-indoline piperidine ring, not a chain of amino acids — and it is in this register only because it is sold, searched and discussed alongside the injectable growth hormone peptides. Its international non-proprietary name is ibutamoren; sellers also call it Nutrobal or Oratrope. It was discovered at Merck in the 1990s, tested in people for muscle loss with age, hip fracture, growth hormone deficiency and Alzheimer's disease, and never approved anywhere. Merck licensed it out in October 2013; it is now in a phase 3 trial in children under the name LUM-201.

Sold as

By mouth, once a day (tablet or capsule).

Legal status in the EU

Not an approved medicine in the EU, the US or anywhere else. It holds an EU orphan designation for growth hormone deficiency (EU/3/17/1882, granted 20 June 2017, sponsor now Agos Healthcare Limited), which is a development incentive and not an authorisation. The US regulator concluded in a warning letter of 19 December 2025 that ibutamoren is excluded from the legal definition of a dietary supplement under section 201(ff)(3)(B)(ii) of the FD&C Act, and has written to sellers stating that their MK-677 products are unapproved new drugs. Sweden's doping law (1991:1969) covers, in its own wording, chemical substances that increase the production or release of growth hormone, and prohibits importing, transferring, manufacturing, offering for sale, possessing and using them outside medical or scientific purposes; no published Swedish decision naming ibutamoren was found in this review. Named directly on the WADA 2026 Prohibited List, section S2.2.4, as "ibutamoren (MK-677)", prohibited at all times.

It switches on the ghrelin receptor — the receptor the hunger hormone uses — in the pituitary gland and the hypothalamus. That makes the gland release more growth hormone in bigger natural bursts, without changing how many bursts there are, and the extra growth hormone makes the liver release more IGF-1. It also makes people hungry, for the same reason. Because it is not a peptide it survives the stomach, which is why it is a tablet rather than an injection.

Part of the bodyWhat happensHow it is knownKind of evidence

The pituitary gland, at the base of the brain

MK-677 fits the receptor that the hunger hormone ghrelin normally uses. That receptor sits on the pea-sized gland under the brain that makes growth hormone, and switching it on makes the gland release more. The natural rhythm survives: growth hormone still comes out in bursts, and the number of bursts does not change — the bursts get bigger and the level between them rises. In healthy 64-to-81-year-olds, 25 mg a day roughly doubled the average amount of growth hormone in the blood over 24 hours within two weeks. In a two-year trial in 60-to-81-year-olds it held it 1.8 times higher than the starting level, which is where a healthy young adult sits.

Measured in 65 healthy adults aged 60 to 81 over two years, with blood taken every 10 minutes for 24 hours at the start and every 6 months, against a dummy tablet. Also measured in 32 healthy people aged 64 to 81 over 14 and 28 days, and in 24 obese men aged 18 to 50.

Measured in people

Source [01]Source [14]Source [15]

The growth signal in the blood (IGF-1)

Growth hormone makes the liver release IGF-1, and it is IGF-1 that actually reaches muscle and bone. This is the part of the story that always works. In healthy older adults IGF-1 rose about one and a half times, into the range of a young adult, and stayed there for two years of daily tablets. In people with Alzheimer's disease it rose 60.1 per cent at six weeks and 72.9 per cent at twelve months. In obese men it rose about 40 per cent in eight weeks. In people on kidney dialysis it rose 65 per cent more than on a dummy tablet. Stopping reverses it: one month after people were switched to a dummy tablet, IGF-1 was back where it started.

Measured in people in every published trial of this compound, including 65 healthy older adults over two years, 563 people with Alzheimer's disease over a year, 24 obese men over eight weeks and 22 people on dialysis in a three-month crossover.

Measured in people

Source [01]Source [02]Source [16]

Muscle — and what that muscle could actually do

This is what people take it for, and it is the part that has been measured most carefully and come out worst. Over a year, fat-free mass — everything in the body that is not fat, mostly muscle and the water inside it — went up 1.1 kg on MK-677 and down 0.5 kg on a dummy tablet. Then the same people were tested. Nobody got stronger at the knee or the shoulder. Nobody walked 30 metres faster, walked further in six minutes, went up or down four flights of stairs quicker, or got out of an armless chair faster. Not one measure of strength or function differed from the dummy group at 6 or at 12 months. The authors say plainly that the study was not long enough or large enough to settle functional questions in healthy older people — but what it measured, it measured, and it found nothing.

Measured in 65 healthy adults aged 60 to 81 for a year, against a dummy tablet, with strength tested on a machine and four timed physical tasks repeated every six months. The same tests were run again at two years in a subgroup of 53 people.

Measured in people

Source [01]

Appetite, and body weight

It makes you hungry, because it is switching on the hunger receptor. Two in three people on MK-677 reported a bigger appetite against one in three on a dummy tablet. In half of them the hunger settled back to normal within three months. Weight went up more than fat-free mass did: 2.7 kg against 0.8 kg on the dummy tablet over a year. Total body fat did not differ between the groups, and neither did the fat around the organs in the belly — but fat on the arms and legs rose 1.1 kg against 0.24 kg. In obese men given it for eight weeks, fat-free mass rose and total and belly fat did not fall.

Measured in 65 healthy adults aged 60 to 81 over a year against a dummy tablet, with body composition measured four different ways including a whole-body scan and a CT slice through the abdomen. Also measured in 24 obese men aged 18 to 50 over eight weeks.

Measured in people

Source [01]Source [15]

Blood sugar and how well insulin works

Blood sugar drifts up and insulin stops working as well. Over a year, fasting blood sugar rose 0.3 mmol/L (5 mg/dL) on MK-677 and did not move on the dummy tablet, and HbA1c — the three-month average of blood sugar — rose 0.2 percentage points. Sixteen of the 43 people on MK-677 crossed from a normal fasting sugar into the 5.6 to 6.1 mmol/L band, against 2 of 22 on the dummy tablet, and six went higher than that. An estimate of how well insulin was working fell in the MK-677 group and not in the other. One 81-year-old man needed his dose cut and a low-carbohydrate diet before his numbers came back. In a shorter study in healthy 64-to-81-year-olds, fasting sugar went from 5.4 to 6.8 mmol/L in four weeks at the same dose.

Measured in 65 healthy adults aged 60 to 81 over one and two years against a dummy tablet, and in 32 healthy people aged 64 to 81 over four weeks. In obese men, fasting sugar and insulin did not change but a sugar-drink test showed worse handling of sugar at two and eight weeks.

Measured in people

Source [01]Source [14]Source [15]

The heart, in frail older people

A trial in older people recovering from a hip fracture was stopped early because of heart failure — the kind where the heart cannot move blood well enough and fluid builds up in the lungs and legs. The published summary says a safety signal appeared in a limited number of participants and does not give the number. The authors' conclusion is one sentence long: in this group of patients, the drug has an unfavourable safety profile. The US regulator repeated the warning in December 2025, listing water retention and a possible increase in the risk of heart failure in certain people among the reasons an unapproved ingredient like this should not be in a supplement. In the earlier two-year trial in healthy older adults, one 68-year-old woman had a heart attack seven days after starting it; with one event in one person, nothing can be concluded from that either way.

Measured in 123 older people recovering from a hip fracture, half on MK-677 and half on a dummy tablet, over 24 weeks, in a trial that was stopped before it finished. The regulator's statement is from a warning letter of 19 December 2025.

Measured in people

Source [01]Source [03]Source [08]

Bone

It speeds bone up in both directions at once — more bone being built and more being broken down — which is not the same as more bone. In 292 women aged 64 to 85 with thin bones, MK-677 raised the markers of bone building by 22 per cent and the markers of bone breakdown by 41 per cent. Added on top of an established osteoporosis drug for 18 months it gave a bigger gain at one site, the neck of the thigh bone, 4.2 per cent against 2.5 per cent — and no advantage at the spine, the whole hip or the whole body. The authors call that lack of benefit elsewhere a concern when weighed against the side effects. In healthy older adults, density at the same thigh-bone site actually fell at 12 months, which is what happens early when bone turnover speeds up.

Measured in 292 women aged 64 to 85 with low bone density in the neck of the thigh bone, in a randomised trial with a dummy tablet running 12 months for the markers and 18 months for the density scans. Also measured in 65 healthy adults aged 60 to 81 over a year.

Measured in people

Source [01]Source [17]

The brain, in Alzheimer's disease

Nothing. The idea was that IGF-1 helps clear the protein that builds up in Alzheimer's disease, and that a tablet raising IGF-1 might slow the illness down. It raised IGF-1 by 72.9 per cent over a year and did not change a single one of the four things that were measured: the doctor's overall impression with input from the carer, the standard test of thinking, the scale of everyday activities, and the dementia rating. This is the largest trial ever run on this compound and it is unambiguous.

Measured in 563 people with mild to moderate Alzheimer's disease, 416 of whom finished, given 25 mg a day or a dummy tablet for 12 months, with neither the participants nor the staff knowing which.

Measured in people

Source [02]Source [18]

Growth, in children who lack growth hormone

This is the one place the compound is still being tested, and the honest summary is that it works and works less well than the injection it would replace. In 104 children who had never been treated, six months of the tablet grew them 6.8, 8.2 or 7.7 centimetres a year depending on the dose, against 10.6 centimetres a year for a daily injection of growth hormone. About three in four children on the two higher tablet doses reached the growth rate the study counted as a good response, against every single child on the injection. A phase 3 trial in 150 children started on 20 May 2026 and is due to report in 2027 or 2028.

Measured in 104 children who had not been treated before, split between three tablet doses and a daily growth hormone injection, over 6 months of a 24-month study, with results posted to the trial registry.

Measured in people

Source [04]Source [05]Source [23]

Sleep

One short study is the whole basis for the sleep claim, and it is a small one. Eight young adults aged 18 to 30 took it at bedtime for seven days at a time; at 25 mg, the deepest stage of sleep lasted about 50 per cent longer and dreaming sleep rose more than 20 per cent, compared with a dummy tablet. Six people aged 65 to 71 took it for 14 days and their dreaming sleep rose by nearly half. That is 14 people in total, measured for a fortnight at most. When the two-year trial in 65 older adults gave people a standard sleep questionnaire every six months, nothing changed on it — nor on any of the other three well-being questionnaires.

Sleep stages were recorded in a laboratory in 8 healthy adults aged 18 to 30 across three 7-day periods, and in 6 people aged 65 to 71 across two 14-day periods. Self-reported sleep quality was tracked for two years in 65 healthy adults aged 60 to 81 against a dummy tablet.

One small study

Source [01]Source [19]

The liver

Two separate things, both unwelcome. In a small hospital study in people with fatty liver disease, the hope was that raising growth hormone would clear fat out of the liver; over six months the fat in the liver went up, not down, in the seven people who finished. Separately, there are published cases of liver damage in people who bought it. A man in his early thirties turned up with disturbed liver blood tests after two months of MK-677, and they went back to normal when he stopped. Of the eleven side-effect reports naming ibutamoren in the US regulator's public file, five describe liver injury, jaundice or cholestasis — though every one of those also names other compounds taken at the same time.

The liver-fat measurements come from an open study of 12 adults with fatty liver disease at a Boston hospital, of whom 7 finished, compared with 10 people from an earlier dummy-tablet group; the difference was not statistically significant. The rest is one published case report and a search of the regulator's voluntary report file, which found 11 reports in total.

One small study

Source [20]Source [21]Source [22]

Two large randomised trials measured what MK-677 was meant to change and found nothing. In 563 people with mild to moderate Alzheimer's disease given 25 mg daily for 12 months, IGF-1 rose 60.1% at six weeks and 72.9% at twelve months, and none of the four disease measures differed from placebo (Sevigny et al., Neurology 2008;71:1702-8). In 123 older people recovering from a hip fracture, IGF-1 rose 51.4 ng/mL more than on placebo, most functional performance measures did not improve, and the trial was stopped early because of a congestive heart failure signal (Adunsky et al., Arch Gerontol Geriatr 2011;53:183-9); an earlier 161-person hip-fracture trial had already found no significant functional benefit (Bach et al., J Am Geriatr Soc 2004;52:516-23). The two-year trial in 65 healthy adults aged 60-81 met one of its two primary endpoints — fat-free mass +1.1 kg versus -0.5 kg on placebo — and missed the other, the deep fat inside the belly, which did not differ from placebo; it reported no change in isokinetic strength or in any of four timed physical tasks, while fasting glucose rose 0.3 mmol/L and HbA1c 0.2 percentage points (Nass et al., Ann Intern Med 2008;149:601-11). It was never approved anywhere. The record is graded "still being tested in people" for one reason only: the same molecule is in an active phase 3 trial as LUM-201, in 150 prepubertal children with growth hormone deficiency (NCT06948214, started 20 May 2026, due 2028) — a different population and a different question from the muscle and anti-ageing uses it is sold for. In that programme's phase 2 study, the tablet grew children 6.8 to 8.2 cm per year against 10.6 cm per year for daily growth hormone injections (NCT04614337, 104 children, results posted).

Growth hormone responds to the first tablet — the biggest single spike is the first dose, and the response settles to a smaller, steady one within a week. IGF-1 climbs over weeks: about 60 per cent by six weeks and about 73 per cent by twelve months in the Alzheimer's trial, and a rise of roughly half in healthy older adults, reached by six months and held for two years. Hunger arrives early and fades in about half of people within three months. Fat-free mass is measurable at six months and does not keep climbing after that. Blood sugar drifts up over the same year. Nothing measured about strength or function ever moved at all, at any timepoint. Stopping undoes it quickly: one month after people were switched to a dummy tablet, IGF-1 was back where it started, and the fat-free mass gain reversed over the following year.

What was measuredWhat happenedIn whomHow it is known

Strength and physical function

No difference from a dummy tablet on any test, at 6 months or at 12. Knee and shoulder strength on a machine: no difference. Walking 30 metres, walking as far as possible in 6 minutes, going up and down four flights of stairs, standing up from a chair five times: no difference. The one measure that came close favoured the drug only as a smaller decline in shoulder strength, and did not reach significance.

65 healthy adults aged 60 to 81, 43 on MK-677 and 22 on a dummy tablet, tested every 6 months for a year.

Measured in people

Source [01]

Alzheimer's disease, on four separate measures

No difference from a dummy tablet on any of them over 12 months, even though IGF-1 rose 60.1 per cent at six weeks and 72.9 per cent at twelve months. The authors' own conclusion is that despite clear evidence the drug reached its target, it was ineffective at slowing the disease.

563 people with mild to moderate Alzheimer's disease randomised to 25 mg daily or a dummy tablet; 416 completed 12 months.

Measured in people

Source [02]

Fat-free mass — muscle and the water inside it

Up 1.1 kg on MK-677 and down 0.5 kg on a dummy tablet at 12 months. Body weight rose 2.7 kg against 0.8 kg. Total body fat did not differ between the groups and neither did the fat around the organs in the belly; fat on the arms and legs rose 1.1 kg against 0.24 kg. The gain held at two years in the people who stayed on it, and reversed in the people switched to a dummy tablet.

65 healthy adults aged 60 to 81, 43 on MK-677 and 22 on a dummy tablet, for 12 months, with a two-year look at 53 of them.

Measured in people

Source [01]

Recovery after a broken hip

Two trials, both essentially negative. In the first, IGF-1 rose 84 per cent against 17 per cent on a dummy tablet and there was no significant difference in any measure of physical function or in the overall sickness score. In the second, IGF-1 rose by 51.4 nanograms per millilitre more than on the dummy tablet, stair-climbing power did not differ, and most other function measures did not either; one measure, walking speed, did favour the drug. The second trial was stopped early over heart failure.

161 people aged 65 and over recruited within 18 days of a hip fracture, treated for 6 months and followed for 6 more (first trial); 123 older people with hip fracture, 62 on MK-677 and 61 on a dummy tablet, over 24 weeks (second trial).

Measured in people

Source [03]Source [13]

Height gained by children who lack growth hormone

The tablet grew children 6.8, 8.2 and 7.7 centimetres a year at the low, middle and high dose; the daily growth hormone injection grew them 10.6 centimetres a year. Counting only children who hit the study's own threshold for a good response, the figures were 44 per cent, 73 per cent and 73 per cent on the tablet against 100 per cent on the injection.

104 prepubertal children with growth hormone deficiency who had never been treated, measured over the first 6 months of a 24-month open study.

Measured in people

Source [05]

Fasting blood sugar, HbA1c and how well insulin works

Fasting blood sugar rose 0.3 mmol/L (5 mg/dL) on MK-677 and did not move on a dummy tablet. HbA1c rose 0.2 percentage points against a fall of 0.1. An estimate of insulin sensitivity fell in the MK-677 group and did not in the other. Sixteen of 43 people on the drug crossed from a normal fasting sugar into the 5.6 to 6.1 mmol/L band, against 2 of 22 on the dummy tablet; four went to between 6.1 and 6.7 and two reached 6.9 mmol/L.

65 healthy adults aged 60 to 81 over 12 months, against a dummy tablet.

Measured in people

Source [01]

Bone density in women with thin bones

Added to an established osteoporosis drug, MK-677 gave 4.2 per cent at the neck of the thigh bone against 2.5 per cent for the osteoporosis drug alone. At the spine, the whole hip and the whole body there was no advantage at all. Markers of bone building rose 22 per cent and markers of bone breakdown rose 41 per cent.

292 women aged 64 to 85 with low bone density, in four groups, for 12 months of treatment and 18 months of density scans.

Measured in people

Source [17]

IGF-1 in people on kidney dialysis

65 per cent higher than on a dummy tablet. Nobody has yet measured whether that translates into more muscle, more strength, a better quality of life or a longer life in this group; the authors say those studies still need doing.

26 people on haemodialysis enrolled, 22 of whom completed a three-month crossover where everyone took both the drug and the dummy tablet.

Measured in people

Source [16]

Fat in the liver, in people with fatty liver disease

It went up, by 3.9 percentage points over six months. The comparison group, taken from an earlier study run the same way, went up 6.6 points. The difference was not statistically significant, and neither were the changes in a scan measure of liver inflammation and scarring or in a liver blood test.

12 adults with a body mass index of 25 or more and fatty liver disease, of whom 7 completed 6 months; everyone knew they were taking the drug, and the comparison group was historical.

One small study

Source [20]

Protein loss during a starvation diet

It stopped it. Over a week of eating far too little, people on MK-677 held a slightly positive nitrogen balance, +0.31 g a day, while people on a dummy tablet lost 1.48 g a day. This is the single clearest positive result in the whole human record for this compound — and it lasted seven days, in eight people, under a diet nobody follows.

8 healthy volunteers aged 24 to 39, on 18 kcal per kg of body weight a day for two 14-day periods, each person taking both the drug and the dummy tablet in turn.

One small study

Source [24]

The serious signal is heart failure: the second hip-fracture trial was stopped early because of it, and its authors concluded that MK-677 has an unfavourable safety profile in that group. Blood sugar drifts up and insulin works less well — 16 of 43 people taking MK-677 in the two-year trial crossed out of the normal fasting range within a year, against 2 of 22 on placebo, and two reached 6.9 mmol/L. Common effects were increased appetite (about 7 in 10 versus about 4 in 10 on placebo, fading in half of people within three months), mild swelling of the legs and transient muscle pain. Published cases of liver damage exist in people who bought it, usually alongside other unapproved compounds. Nobody has been followed beyond two years, so the two questions that matter most — diabetes and cancer, given that it holds IGF-1 at a young adult level indefinitely — are unanswered. European medicines control laboratories analysing 324 seized performance-enhancing samples over five years found ibutamoren more often than any other molecule, and the US regulator has found it undeclared in a supplement sold to parents for children's height.

EffectWhat it feels likeHow often

Heart failure in older people recovering from a hip fractureSerious

Heart failure is when the heart cannot pump well enough and fluid backs up into the lungs and the legs. The trial was ended before it finished and the authors concluded in one sentence that MK-677 has an unfavourable safety profile in this group of patients. The US regulator restated the concern in December 2025, naming water retention and a possible increase in the risk of heart failure in certain people. The earlier hip-fracture trial had excluded anyone who already had heart failure, so this is not something these programmes were designed to find.

Not stated as a number. The published summary says only that a safety signal appeared in a limited number of patients and that the trial was stopped because of it. The full paper is behind a paywall this review could not open, so the count in each group is not reported here.

Source [03]Source [08]Source [13]

Liver damage in people who bought it themselvesSerious

A man in his early thirties developed disturbed liver blood tests after two months of MK-677 and they returned to normal after he stopped. Of the 11 reports naming ibutamoren in the US regulator's public file, five describe liver injury, jaundice or cholestasis — bile backing up in the liver. Every one of those also names other compounds alongside it, so the reports cannot separate what caused what. A published self-experiment in one 25-year-old man who took MK-677 with the muscle drug LGD-4033 for five weeks recorded liver enzymes rising 96 and 205 per cent, and returning to normal afterwards; he was taking both.

Not measured. No trial reported a liver signal; the trials monitored routine blood tests and did not flag one. What exists outside the trials is one published case and a handful of voluntary reports.

Source [21]Source [22]Source [25]

Cancers diagnosed during the two-year trialSerious

An 82-year-old woman on MK-677 was diagnosed with a tongue cancer at 12 months; a man on the dummy tablet was diagnosed with a kidney cancer at 6 months; an 83-year-old woman was diagnosed with a bowel cancer at the end of year two. All were withdrawn. Nothing can be concluded from three cancers in 65 older people over two years, and that is the point: this compound raises IGF-1, a signal that tells cells to grow, for as long as you take it, and no study of a size or length that could answer the cancer question has ever been done.

Three cancers among 65 people over two years: one on MK-677, one on a dummy tablet, and one in a person who had taken MK-677 in year one and a dummy tablet in year two.

Source [01]

Being hungry all the time

This is not a side effect in the usual sense — it is the drug doing what it does, since it switches on the receptor the hunger hormone uses. It is also why weight went up more than muscle did.

About 7 in 10 people on MK-677 against about 4 in 10 on a dummy tablet, in the two-year trial. In half of them it settled back to normal within three months, and more slowly in the rest.

Source [01]Source [08]

Blood sugar creeping up

Small on average and not small for everyone. Six people went well past the first threshold, two of them to 6.9 mmol/L, which is at the edge of a diabetes diagnosis. An 81-year-old man needed his dose reduced and a low-carbohydrate diet. In a separate four-week study in healthy people aged 64 to 81, fasting sugar went from 5.4 to 6.8 mmol/L at the same dose. Nobody has followed anyone for long enough to say whether this becomes diabetes.

Sixteen of 43 people on MK-677 crossed out of the normal fasting range in a year, against 2 of 22 on a dummy tablet. Average fasting sugar rose 0.3 mmol/L and HbA1c 0.2 percentage points, both statistically significant.

Source [01]Source [14]

Swollen ankles and legs

Fluid holding in the lower legs is a known effect of raising growth hormone and is on the label of the approved injectable growth hormone medicines. It matters more than the numbers suggest in older people, because it is also the thing that goes wrong first when a weak heart starts to fail.

About 4 in 10 people on MK-677 against about 3 in 10 on a dummy tablet in the two-year trial, a difference that did not reach statistical significance. Described as mild and passing.

Source [01]Source [08]

Aching muscles

Joint pain was reported by more than half of both groups and did not differ between them, so it cannot be pinned on the drug in this study. In the children's trial, one child on the middle dose had pain in an arm or leg badly enough for it to be recorded as a serious event.

About 1 in 3 people on MK-677 against about 1 in 11 on a dummy tablet in the two-year trial; the difference did not reach statistical significance in a study of this size. Described as passing.

Source [01]Source [05]

A small rise in the stress hormone cortisol

Short studies of a week to two months found no rise at all, and the authors of the two-year trial did not think this rise explained the change in blood sugar. It is recorded here because it is one of the few blood measurements this compound moves that people do not talk about.

Measured, and small: an average rise of 47 nanomoles per litre over a year on MK-677, against a slight fall on a dummy tablet.

Source [01]Source [15]

Anything that takes longer than two years to appear

The two things a longer study would be looking for are diabetes and cancer, because this compound raises blood sugar and holds IGF-1 — a signal that tells cells to divide — at a young adult level for as long as it is taken. Neither question has been asked at the size and length needed to answer it. The regulator's own phrasing in December 2025 is that the long-term effects of ibutamoren are unknown and may pose additional health risks.

Not measured. Two years is the longest anyone has been followed in a published study, and that was 53 people.

Source [01]Source [08]

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.

Nass and colleagues 2008 — the two-year trial in healthy older adults, the one people cite for muscle

25 mg once a day, by mouth, or a matching dummy tablet.

12 months for the main results, with a second year in 53 of the participants.

Source [01]

Sevigny and colleagues 2008 — Merck's Alzheimer's disease trial, the largest trial ever run on this compound

25 mg once a day, by mouth, or a matching dummy tablet.

12 months.

Source [02]

Chapman and colleagues 1996 — the dose-finding study in healthy people aged 64 to 81

2, 10 or 25 mg once a day, by mouth, or a dummy tablet. The effect on growth hormone tracked the dose, and at 25 mg the reported IGF-1 level returned to the young adult range.

Two separate periods of 14 and 28 days.

Source [14]

Copinschi and colleagues 1997 — the sleep study that the sleep claim rests on

5 or 25 mg at bedtime in young adults; 2 then 25 mg at bedtime in older adults; and a dummy tablet.

Three 7-day periods in the young adults, two 14-day periods in the older adults.

Source [19]

Chapman and colleagues 1997 — nine men who had been treated for growth hormone deficiency as children

10 or 50 mg once a day, by mouth, or a dummy tablet.

Four days in each of two periods at least 28 days apart.

Source [26]

The children's programme, run today as LUM-201 — a phase 2 study against daily growth hormone injections, and the phase 3 trial that started in May 2026

0.8, 1.6 or 3.2 mg per kilogram of body weight a day by mouth in the phase 2 study, against 34 micrograms per kilogram a day of injected growth hormone. The phase 3 trial gives 1.6 mg per kilogram a day or a matching dummy capsule.

24 months in the phase 2 study, with the comparison against injections read at 6 months. 12 months in the phase 3 trial, which is due to finish in early 2028.

Source [04]Source [05]

What people report

• What it does in a young, trained person lifting weights — the group that buys it has never been studied, at any dose, for any length of time.
• Whether the fat-free mass it adds is muscle that works: the one trial that measured strength and physical function alongside it found no change in either.
• How many people developed heart failure in the hip-fracture trial that was stopped because of it — the published summary says only that it was a limited number.
• Whether the rise in blood sugar becomes diabetes with years of use: nobody has been followed for more than two years.
• Whether holding IGF-1 at a young adult level indefinitely affects the risk of cancer — no study of a size or length that could answer this has been done.
• What happens after two years, which is as long as any published study has run, in 53 people.
• Whether it helps any injury heal — never measured, in any study.
• Whether it does anything for sleep beyond a fortnight: the sleep study ran seven to fourteen days in 14 people, and the two-year trial's sleep questionnaire showed no change.
• What it does when taken with the muscle drugs it is usually sold beside — no published study has given a person both, and 10 of the 11 reports that reach the US regulator name several compounds at once.
• Whether the published cases of liver damage were caused by MK-677 or by what was taken with it.
• Whether men and women respond differently: the two-year trial recruited men and women separately by design and never reported a result by sex.
• What is actually in the products sold online: the analyses that exist are of samples seized by medicines agencies, not of anything bought as a customer.
• Whether it is safe in anyone with heart disease, diabetes, cancer or uncontrolled high blood pressure — every trial excluded them.
• Why Merck abandoned it: no statement from the company giving a reason could be found, and every explanation circulating online traces back to sellers.
• Whether the children's programme will show it works: the phase 3 trial began on 20 May 2026 and is due to finish in early 2028.

Does MK-677 work?

It depends entirely on what you mean by work. It raises growth hormone and IGF-1 every single time, in everyone, for as long as you take it — that part is not in doubt. What it has failed to do is change anything that matters to a person. Over a year in healthy 60-to-81-year-olds it added about a kilo of fat-free mass and made nobody stronger and nobody faster at walking, stairs or standing up. Over a year in 563 people with Alzheimer's disease it did nothing at all to the disease. Two trials in people recovering from a hip fracture failed their main tests.

Source [01]Source [02]Source [03]

Does MK-677 build muscle?

It increases fat-free mass, which is not quite the same thing. In the two-year trial, fat-free mass went up 1.1 kg while the dummy group lost 0.5 kg — but fat-free mass includes the water inside cells, and the water inside cells went up too. The same people were then tested on a strength machine and on four timed physical tasks, and nothing improved. No published study has ever given MK-677 to a young, trained person lifting weights, so what it does in the group that actually buys it has never been measured.

Source [01]Source [15]

Is MK-677 legal?

It is not an approved medicine anywhere in the world, so it cannot legally be sold to the public as a medicine or as a supplement in the EU or the US. The US regulator has ruled that ibutamoren is excluded from the legal definition of a dietary supplement, because it was investigated as a new drug first, and has written to sellers telling them their MK-677 products are unapproved new drugs. Sweden's doping law covers, in its own words, chemical substances that increase the production or release of growth hormone, and forbids importing, selling, possessing and using them outside medical or scientific purposes; that description fits ibutamoren, though this register found no published Swedish decision naming it.

Source [08]Source [09]Source [12]

What are the side effects of MK-677?

The common ones in the trials were hunger (about 7 in 10 people, fading in half of them within three months), swollen ankles, aching muscles, and blood sugar drifting up — 16 of 43 people crossed out of the normal fasting range within a year. The serious one is heart failure: a trial in older people recovering from a hip fracture was stopped early because of it. Outside the trials there are published cases of liver damage in people who bought it, though those people were usually taking several other compounds too.

Source [01]Source [03]Source [21]

MK-677 vs growth hormone injections — which is stronger?

The injection, and there is a head-to-head trial that says so. In 104 children who lack growth hormone, six months of daily MK-677 tablets grew them 6.8 to 8.2 centimetres a year depending on the dose; daily growth hormone injections grew them 10.6 centimetres a year. Every child on the injection reached the study's threshold for a good response; on the best tablet dose, about three in four did. The tablet is being developed as a more convenient option for a subgroup of patients, not as a stronger one.

Source [05]Source [23]

Is MK-677 a SARM?

No, and it is not a peptide either. SARMs act on the receptor that testosterone uses; MK-677 acts on the receptor the hunger hormone ghrelin uses, and its whole effect runs through growth hormone. It gets called a SARM because it is sold in the same shops, on the same pages, by the same people. A US laboratory study bought 44 products advertised as SARMs and found that 17 of them contained a different unapproved drug instead — ibutamoren among them.

Source [11]Source [27]

Can you buy MK-677, and is what you get real?

It is sold widely online, labelled for research, and European medicines agencies have been pulling it off that market for years. Across five years, 14 official laboratories in 13 countries analysed 324 seized samples of muscle-building products; of 18 different molecules found, ibutamoren was the most common one. Most of the samples contained an active dose and some were overdosed. Two out of three seized products were presented as medicines and one in four as dietary supplements, which the authors flag because a buyer of the second kind does not know they are taking an unapproved pharmaceutical.

Source [08]Source [10]Source [27]

Is MK-677 banned in sport?

Yes, at all times, in competition and out of it. The 2026 prohibited list names it directly — ibutamoren (MK-677) — in section S2.2.4, among growth hormone secretagogues, alongside anamorelin, ipamorelin, ghrelin, macimorelin and tabimorelin. Substances in that class are non-specified, which means a positive test carries the heavier default sanction. It is also detectable: a published method finds it in hair four weeks after a single 10 mg dose.

Source [06]Source [28]

Why did Merck stop developing it?

Merck ran it through trials for muscle loss with age, recovery from hip fracture, growth hormone deficiency and Alzheimer's disease, and it was never approved anywhere. The trials that finished did not show a clinical benefit, and the last hip-fracture trial was stopped early over heart failure. No statement from Merck itself giving a reason could be found. In October 2013 Merck licensed the compound out to a small company, which sold it on in 2018 to the company now running the children's trials.

Source [02]Source [03]Source [29]

1. [01]Nass R et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med 2008;149(9):601-11 (65 adults aged 60-81, two years; free full text) (2008)
2. [02]Sevigny JJ et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial. Neurology 2008;71(21):1702-8 (563 patients, 25 mg daily, 12 months) (2008)
3. [03]Adunsky A et al. MK-0677 (ibutamoren mesylate) for patients recovering from hip fracture: a multicenter, randomized, placebo-controlled phase IIb study. Arch Gerontol Geriatr 2011;53(2):183-9 (123 patients; terminated early for a congestive heart failure signal) (2011)
4. [04]Phase 3 Study of LUM-201 (ibutamoren) in Children With Growth Hormone Deficiency (NCT06948214, Lumos Pharma, 150 planned, recruiting, started 20 May 2026) (2026)
5. [05]Phase 2 Study of Daily Oral LUM-201 in Treatment-Naive Prepubertal Children With Growth Hormone Deficiency (NCT04614337, 104 children, results posted: 6.8-8.2 cm/yr on tablet vs 10.6 cm/yr on injected rhGH) (2024)
6. [06]WADA World Anti-Doping Code International Standard, Prohibited List 2026 — section S2.2.4 names ibutamoren (MK-677) among growth hormone secretagogues (in effect 1 January 2026) (2026)
7. [07]EMA: EU/3/17/1882 — orphan designation for ibutamoren mesilate for the treatment of growth hormone deficiency, granted 20 June 2017 (not a marketing authorisation) (2017)
8. [08]FDA warning letter to Agebox Inc., 19 December 2025 — undeclared ibutamoren mesylate confirmed by laboratory analysis in a children's growth supplement; FDA concludes ibutamoren is excluded from the dietary supplement definition (2025)
9. [09]FDA warning letter to Dynamic Health Group dba SARMS AMERICA, 12 December 2025 — "MK-677 Ibutamoren" named as an unapproved new drug (2025)
10. [10]Barrios MM et al. SARMs, metabolic modulators and growth hormone secretagogues in suspected illegal medicines bought as sport performance enhancers: a study within the GEON network. Drug Test Anal 2025;17(10):2078-85 (324 samples, 14 laboratories, 13 countries; ibutamoren the most frequently found molecule) (2025)
11. [11]PubChem: ibutamoren (CID 178024) — C27H36N4O5S, 528.7 g/mol, a spiro-indoline piperidine small molecule, not an amino-acid chain
12. [12]Swedish law (1991:1969) on the prohibition of certain doping agents — covers chemical substances that increase the production or release of growth hormone (Riksdagen, in Swedish) (1991)
13. [13]Bach MA et al. The effects of MK-0677, an oral growth hormone secretagogue, in patients with hip fracture. J Am Geriatr Soc 2004;52(4):516-23 (161 patients; IGF-I +84% vs +17% on placebo; no significant difference in functional performance or overall SIP-NH) (2004)
14. [14]Chapman and colleagues, stimulation of the GH-IGF-I axis by daily oral MK-677 in healthy elderly subjects (J Clin Endocrinol Metab) (1996)
15. [15]Svensson and colleagues, two-month treatment of obese subjects with oral MK-677 increases GH secretion, fat-free mass and energy expenditure (J Clin Endocrinol Metab) (1998)
16. [16]Campbell and colleagues, oral ghrelin receptor agonist MK-0677 increases serum IGF-1 in hemodialysis patients: a randomized blinded study (Nephrol Dial Transplant, free full text) (2018)
17. [17]Murphy and colleagues, effect of alendronate and MK-677 individually and in combination on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women (J Clin Endocrinol Metab) (2001)
18. [18]Merck trial of MK-0677 in Alzheimer's disease (NCT00074529, protocol 0677-030, 512 people recorded, completed January 2006, no results posted) (2006)
19. [19]Copinschi and colleagues, prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man (Neuroendocrinology) (1997)
20. [20]The impact of ibutamoren on non-alcoholic fatty liver disease: a pilot study (NCT05364684, 12 enrolled, 7 completed, results posted) (2024)
21. [21]Cobani and colleagues, hepatotoxicity induced by MK-677 (BMJ Case Reports) (2025)
22. [22]Side-effect reports naming ibutamoren in the FDA adverse event database (openFDA query, 11 reports)
23. [23]Bright and Thorner, a GH secretagogue receptor agonist (LUM-201) elicits greater GH responses than standard GH secretagogues in a paediatric GH deficiency trial (Horm Res Paediatr, free full text) (2022)
24. [24]Murphy and colleagues, MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism (J Clin Endocrinol Metab) (1998)
25. [25]Cardaci and colleagues, LGD-4033 and MK-677 use impacts body composition, circulating biomarkers and skeletal muscle androgenic hormone and receptor content: a case report (Exp Physiol) (2022)
26. [26]Chapman and colleagues, oral MK-677 stimulates the GH/IGF-I axis in selected GH-deficient adults (J Clin Endocrinol Metab) (1997)
27. [27]Van Wagoner and colleagues, chemical composition and labeling of substances marketed as selective androgen receptor modulators and sold via the internet (JAMA, free full text) (2017)
28. [28]Kintz, knowing the minimal detectable dose can facilitate the interpretation of a hair test result: case example with ibutamoren (MK-677) (Clin Chim Acta) (2026)
29. [29]Lumos Pharma annual report (Form 10-K, financial year 2022) — LUM-201 acquired from Ammonett Pharma in July 2018, licensed from Merck Sharp and Dohme in October 2013 (2023)