Adverse effect · MK-677 (ibutamoren)

How common is adverse effects with MK-677 (ibutamoren)?

B
Grade B — probable, not settledSame RCTs · effect size: moderate · adverse
Short answerProbable, not settled. Human data exist (Same RCTs) and mostly agree, showing a moderate effect — but too few, too small, or not yet peer-reviewed for a firm answer. 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.

What the studies show

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.

Human trials exist and mostly agree, but there are too few of them, they are too small, or one big one is still reading out. Expect the grade to move.

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In context

MK-677 is a small molecule, not a peptide, that mimics the hunger hormone ghrelin and raises growth hormone and IGF-1 when taken by mouth. Unusually for a grey-market compound, it has been through proper trials. In 65 healthy older adults over a year it raised fat-free mass by about 1.1 kg against a 0.5 kg loss on placebo, with no change in total or visceral fat. In 563 people with Alzheimer's disease it raised IGF-1 by 73% and did nothing for the disease. It has never been approved anywhere and is prohibited in sport.

MK-677 (ibutamoren) is not approved. Legal status differs by country — see the regulation section or the jurisdiction pages.

Questions

Is MK-677 (ibutamoren) proven to cause adverse effects?
Not yet settled. Same RCTs — LYO grades it B, meaning probable but liable to change as trials read out.
What studies are behind the grade?
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.
Is MK-677 (ibutamoren) approved for this?
No. MK-677 (ibutamoren) is not approved; it is not an approved medicine for any indication in the jurisdictions LYO covers.

Other outcomes for MK-677 (ibutamoren)

Written and maintained by LYO Research — how pages are written and checked. Reviewed 10 September 2026. Grades count human evidence only; see how LYO grades. Not medical advice. Correct this page →