Summary
MK-677 (ibutamoren) is an orally active small molecule that mimics ghrelin and raises growth hormone and IGF-1. In a two-year randomized trial in healthy older adults, it increased fat-free mass but also raised fasting glucose and reduced insulin sensitivity.
How it works
Ibutamoren activates GHS-R1a and has a long enough half-life for once-daily oral use, producing sustained increases in GH pulse amplitude and IGF-1.
Research use cases
Areas where MK-677 has been studied. Inclusion here does not mean it works for that purpose.
- Age-related decline in GH and muscle mass
- Recovery after hip fracture (phase 2b)
- Diagnostic and pharmacology research
What the research found
Healthy older adults (2 years)
In 65 adults aged 60 to 81, ibutamoren raised IGF-1 to young-adult levels and increased fat-free mass by about 1.1 kg versus a loss on placebo. Fasting glucose rose and insulin sensitivity fell; appetite increased.1
Hip fracture recovery
A multicentre phase 2b study in older patients recovering from hip fracture was stopped early after a higher rate of congestive heart failure in the treatment group. Functional benefits were not clearly demonstrated.2
Safety and open questions
Increased appetite, fluid retention, muscle pain, raised fasting glucose and reduced insulin sensitivity. A signal for heart failure in frail older adults led to an early trial stop.
Regulatory status
Not approved. Investigated by Merck in the 1990s and 2000s. Prohibited by WADA.
Status was accurate when this page was last reviewed on October 26, 2026. Regulations change; check with the relevant authority before relying on it.
MK-677: common questions
Is MK-677 a SARM or a peptide?
Neither. It is a non-peptide small molecule that acts on the ghrelin receptor. It is listed here because it shares a mechanism with peptide GH secretagogues.
Is MK-677 approved for human use?
Not approved. Investigated by Merck in the 1990s and 2000s. Prohibited by WADA.
References
- Nass R, Pezzoli SS, Oliveri MC, et al. (2008). Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Annals of Internal Medicine.
- Adunsky A, Chandler J, Heyden N, et al. (2011). 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.
Links open a PubMed search for the exact title, or the original source where one is given.