Menu

MK-677 (Ibutamoren): What the Trials Found

By Evan Marsh, EditorUpdated Sources: randomized controlled trials and case reports

MK-677 is the rare compound in this catalog with a real clinical record — Merck ran it through late-stage trials in several populations. That record is also the reason to approach it carefully, because what those trials found is more complicated than the marketing suggests: the drug does exactly what it says to hormone levels, and repeatedly failed to convert that into clinical benefit.

First, a category note. MK-677 is not a peptide. It is an orally active small molecule that activates the ghrelin receptor. It appears in peptide catalogs because it raises growth hormone, which puts it alongsidesermorelin andCJC-1295 + ipamorelin in how people use it — but it is a different kind of drug, taken by mouth.

How it works

Ghrelin is the hormone that signals hunger and also triggers growth hormone release. MK-677 mimics it at the receptor, producing a sustained increase in GH pulse amplitude and, downstream, in IGF-1. Because it is orally bioavailable and long-acting, one daily dose maintains the elevation — the practical advantage that made it attractive as a drug and keeps it popular now. The appetite stimulation is not a side effect of the mechanism; it is the mechanism.

What the trials found

Body composition — the two-year trial

The central study: 65 healthy adults aged 60–81, randomized to 25 mg daily or placebo for two years. MK-677 significantly raised GH and IGF-1 and increased fat-free mass compared with placebo. Alongside that, fasting glucose and cortisol rose modestly, and increased appetite and lower-limb oedema were common.

Two honest readings of that result. It is a genuine, placebo-controlled, two-year demonstration of a body-composition effect — better evidence than almost anything else on this site. And fat-free mass is not muscle: it includes body water, in a drug that measurably causes fluid retention, and the trial did not demonstrate improved strength or physical function.

Alzheimer's disease — a clean negative

563 patients with mild-to-moderate Alzheimer's, 12 months, double-blind and placebo-controlled. MK-677 raised IGF-1 by 60–73% and produced no significant difference on any cognitive or functional measure. The authors concluded it was ineffective at slowing progression. This trial is the most useful thing in the MK-677 literature, because it separates the hormonal effect from the clinical one so cleanly.

Hip fracture recovery — stopped early

A phase 2b trial in 123 elderly patients recovering from hip fracture found a modest gait-speed improvement and no improvement across several other functional measures. The trial was terminated early because of a congestive heart failure safety signal in a limited number of patients. That is the single most important safety datapoint about this compound, and it rarely appears in vendor descriptions.

Other findings

Earlier work showed MK-677 reversed the nitrogen loss caused by dietary restriction — the nitrogen-balance study behind its muscle-preservation reputation — and a small polysomnography study reported improved sleep quality measures. Bone-turnover studies in postmenopausal osteoporosis were also run.

Side effects and monitoring

  • Increased appetite — pronounced, and the reason it is unsuitable for anyone whose goal is fat loss.
  • Lower-limb oedema and joint discomfort — consistent across trials, dose-related.
  • Fasting glucose and insulin sensitivity — modest deterioration in the two-year trial; anyone with prediabetes or diabetes should treat this as the primary concern.
  • Cortisol — modest increases reported.
  • Cardiac — the hip-fracture trial's congestive heart failure signal in a vulnerable population.
  • Liver — a 2025 case report documents transaminitis in a healthy man in his early 30s after two months of use, resolving after discontinuation. A single case does not establish incidence, but it is on the record.

The class-level caution applies as it does to every GH-axis compound: sustained IGF-1 elevation is not a neutral state in the presence of an undiagnosed malignancy. Oursafety overview covers how these risks compare across compounds.

Regulatory status

  • Not FDA approved for any indication, despite reaching phase 2 and 3 trials.
  • Not a dietary supplement. It is frequently sold as one, which FDA has treated as unlawful marketing of an unapproved drug.
  • WADA prohibits growth hormone secretagogues including ibutamoren under section S2; it is detectable in hair testing, and a 2026 forensic paper documents the method.

Research on MK-677 (Ibutamoren)

7 records in our research database, classified by evidence type:

Browse all MK-677 (Ibutamoren) research →

Frequently asked questions

What is MK-677?

MK-677 (ibutamoren) is an orally active ghrelin receptor agonist developed by Merck. It is not a peptide — it is a small molecule that mimics ghrelin, causing the pituitary to release growth hormone. It reached late-stage clinical trials for several indications and was never approved for any of them.

Does MK-677 build muscle?

The two-year randomized trial in healthy older adults found increased fat-free mass versus placebo, but no demonstrated improvement in strength or function. Fat-free mass includes water, and MK-677 causes fluid retention — which is why the distinction between mass and performance matters here more than usual.

What are the side effects of MK-677?

The trials consistently report increased appetite, lower-limb oedema and modest rises in fasting glucose and cortisol. The hip-fracture trial was stopped early over a congestive heart failure signal in a small number of patients. A 2025 case report documents liver enzyme elevation that resolved after stopping.

Is MK-677 legal?

It is not FDA approved for any indication and is sold as a research chemical, frequently and illegally marketed as a dietary supplement. It is prohibited for tested athletes under WADA section S2 as a growth hormone secretagogue.

Does MK-677 raise IGF-1?

Reliably, and substantially — the Alzheimer's trial recorded 60–73% increases. That trial is also the clearest evidence that raising IGF-1 is not a clinical benefit in itself: despite those increases, MK-677 made no difference to disease progression on any measure.

Sources

  • Nass R et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Annals of Internal Medicine, 2008. PubMed
  • Sevigny JJ et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial. Neurology, 2008;71(21):1702–1708. PubMed
  • Adunsky A et al. MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture: a multicenter, randomized, placebo-controlled phase IIb study. Archives of Gerontology and Geriatrics, 2011. PubMed
  • Murphy MG et al. MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. Journal of Clinical Endocrinology & Metabolism, 1998. PubMed
  • Copinschi G et al. Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man. Neuroendocrinology, 1997. PubMed
  • Murphy MG et al. Effect of alendronate and MK-677 on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women. Journal of Clinical Endocrinology & Metabolism, 2001. PubMed
  • Cobani E et al. Hepatotoxicity induced by MK-677. BMJ Case Reports, 2025;18(7):e265728. PubMed
  • World Anti-Doping Agency. Prohibited List 2026, section S2. WADA Prohibited List

Related guides

Research use only. MK-677 is not approved for human use and is not a dietary supplement. This page summarizes published trial data and is not medical advice.