What the human research shows
The rare grey-market compound where the question has actually been asked and answered. The answer is: a real but modest gain in lean tissue, no fat loss, higher appetite, and higher blood glucose — for a molecule with no approval, no long-term safety file and a sport ban.
Evidence profile0–5
- Metabolic & weightB0.0
- Cardiovascular—0.0
- Muscle & growthA5.0
- Healing & repair—0.0
- Neuro & sleep—0.0
- Immune & inflammation—0.0
- Sexual & hormonal—0.0
- Skin & appearance—0.0
- Ageing & longevity—0.0
| Outcome | Grade | Effect size | Human studies | Where the evidence comes from |
|---|---|---|---|---|
| Growth hormone / IGF-1 elevation | AEstablished | Large | Multiple RCTs | Oral daily dosing reliably restores growth hormone and IGF-1 in older adults to the levels of healthy young adults, and raised IGF-1 by 60–73% in a 563-person trial. This effect is not in dispute.12 |
| Lean mass (older adults) | BProbable | Small | 1 RCT (n=65, 12 months) | Fat-free mass rose by about 1.1 kg over a year against a 0.5 kg loss on placebo — a real difference, in one trial, in people over 60. Whether that becomes strength or function was not shown; the authors themselves called for functional studies.1 |
| Fat loss | BProbable | Not measurable | 1 RCT (n=65) — no effect | Neither total fat mass nor abdominal visceral fat changed over a year; limb fat actually rose more on MK-677 than on placebo. Sold for fat loss, it did the opposite in the one trial that measured it.1 |
| Alzheimer's disease progression | AEstablished | Not measurable | 1 RCT (n=563, 12 months) — negative | A year of 25 mg daily in mild-to-moderate Alzheimer's raised IGF-1 substantially and changed none of the four clinical measures. A clean negative: the target was engaged, and it made no difference.2 |
| Adverse effectsadverse | BProbable | Moderate | Same RCTs | Increased appetite, fluid retention and oedema, muscle pain, and rises in fasting glucose and insulin resistance are reported consistently, as with any sustained growth-hormone elevation. The trials were one to two years; there is no data beyond that.12 |
Literature searched to 10 September 2026. Human studies only; animal and cell work informs the mechanism section and nothing else.
Registered trials
ClinicalTrials.gov lists 6 interventional studies naming MK-677 (ibutamoren) as an intervention — 4 completed, and 1 with results posted to the registry.
A registration is not a result. Anyone can register a study, and many never report — so this list shows what has been attempted, not what has been shown. The graded evidence above is the answer to whether something works.
| Study | Phase | Status | Participants | Sponsor | Results |
|---|---|---|---|---|---|
| Growth Hormone Secretagogue MK-0677 Effect on IGF-1 Levels in ESRD PatientsNCT00395291 · started Aug 2006 | N/A | Completed | 49 | University of Virginia | Posted |
| Study of MK0677 for the Treatment of Alzheimer's Disease (0677-030)(COMPLETED)NCT00074529 · started Oct 2003 | Phase 2 | Completed | 512 | Merck Sharp & Dohme LLC | None |
| Treatment of Sarcopenia in Post-Hip Fracture Patients (0677-032)NCT00128115 · started Sept 2005 | Phase 2 | Terminated | 83 | Merck Sharp & Dohme LLC | None |
| Efficacy and Safety of an Oral Growth Hormone Drug in the Treatment of FibromyalgiaNCT00116129 · started Jul 2005 | Phase 2 | Completed | 64 | Bennett, Robert, M.D. | None |
| Growth Hormone Secretagogue MK-0677's Effect on Lean Body Mass in Chronic Kidney Disease Stage 4/5 SubjectsNCT01343641 · started Mar 2009 | Phase 2 | Withdrawn | 0 | University of Virginia | None |
| Effects of an Oral GH Secretagogue (MK-677) on Body Composition and Functional Ability of Older AdultsNCT00474279 · started Jul 1998 | Phase 1 | Completed | 72* | University of Virginia | None |
Participant counts marked * are the sponsor's estimate, not a final enrolment. Source: ClinicalTrials.gov, read directly from the registry and refreshed weekly.
What it is
MK-677 was developed by Merck in the 1990s as an oral alternative to growth-hormone injections. It is a spiroindoline, not a peptide, which is why it survives digestion and is taken as a capsule or liquid. It is grouped here with the growth-hormone-releasing peptides because it acts on the same ghrelin receptor and is sold into the same market.
It never reached approval. Merck stopped development; a later programme for hip-fracture recovery and another for Alzheimer's did not succeed. What survived is the trial data, and a large grey market that quotes the lean-mass result and not the fat result.
How it is thought to work
It binds the ghrelin receptor in the pituitary and hypothalamus, increasing the size of growth-hormone pulses without abolishing their rhythm. IGF-1 rises in response and stays elevated with daily dosing, unlike the short-acting peptide secretagogues.
The same receptor drives hunger, which is why appetite reliably rises — a feature for the frail patients it was developed for, and the reason 'fat loss' was never a plausible claim.
What is still unknown
- Whether the lean-mass gain in older adults translates into strength or function — the trial did not show it.
- Long-term safety of sustained IGF-1 elevation with years of use; the longest trial was two years.
- What is actually in the products sold as MK-677, since there is no approved manufacturer.
The molecule and how long it lasts
- Formula
- C27H36N4O5S
- Molecular weight
- 528.7 g/mol
- CAS number
- 159634-47-6
- PubChem
- CID 178024
PubChem record, read 23 September 2026.
- Route
- Oral, once daily in the trials
- Half-life
- Taken by mouth daily in year-long trials; no primary half-life figure was found in the accessible literature (the '24 hours' repeated online could not be traced to a source)
From a published human pharmacokinetic study: Copinschi G, et al. Effects of a 7-day treatment with a novel, orally active, growth hormone secretagogue, MK-677, in normal young men. J Clin Endocrinol Metab 1996;81:2776
Regulatory status
No marketing authorisation in any member state. Supplying it for human use is an offence under national medicines law.
Never approved; development discontinued. Sold as a 'research chemical'. Not a lawful dietary-supplement ingredient.
No MHRA licence; supply for human use is an offence.
Not on the ARTG; imports are seized.
No Drug Identification Number.
Named on the Prohibited List among growth-hormone secretagogues, in and out of competition.
Questions people actually ask
Does MK-677 build muscle?
Does MK-677 burn fat?
Is MK-677 a peptide?
Is MK-677 legal?
One page per claimed effect
- ADoes MK-677 (ibutamoren) help with growth hormone / IGF-1 elevation?Multiple RCTs
- BDoes MK-677 (ibutamoren) help with lean mass?1 RCT (n=65, 12 months)
- BDoes MK-677 (ibutamoren) help with fat loss?1 RCT (n=65) — no effect
- ADoes MK-677 (ibutamoren) help with alzheimer's disease progression?1 RCT (n=563, 12 months) — negative
- BHow common is adverse effects with MK-677 (ibutamoren)?Same RCTs
References
- 1Nass R, Pezzoli SS, Oliveri MC, 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):601–61165 adults aged 60–81; two years, primary analysis at one year.
- 2Sevigny JJ, Ryan JM, Van Dyck CH, et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial.Neurology, 2008563 patients; 12 months; negative on all four clinical measures.
- 3World Anti-Doping Agency. The Prohibited List — S2: peptide hormones, growth factors, related substances and mimetics.WADA, current listGrowth-hormone secretagogues, ibutamoren named.
Change log
- 2026-09-10Initial publication. Grade B for lean mass on one 12-month RCT; fat loss and Alzheimer's carry high-certainty null results (effect none).