MK-677

What it is

MK-677, also called ibutamoren, is an orally active compound originally developed by Merck. It is not a peptide, but it is grouped with the growth hormone secretagogue peptides because it acts on the same receptor as ipamorelin and the hormone ghrelin.

How it works

MK-677 activates the ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus, which triggers growth hormone release and raises IGF-1. Because ghrelin is also a hunger hormone, increased appetite is a common effect.

What the research shows

• In a two-year trial in healthy older adults, daily MK-677 raised growth hormone and IGF-1 to levels typical of young adults and increased fat-free mass. Appetite increased, fasting blood sugar rose and insulin sensitivity fell (Nass et al., Annals of Internal Medicine, 2008).
• A trial in older adults recovering from hip fracture raised IGF-1 but did not improve most functional measures, and it was stopped early because of a safety signal of congestive heart failure in a small number of patients (Adunsky et al., 2011).
• It has not been approved for any condition.

Regulatory status

Not approved for any use. It is sold as a research chemical, and growth hormone secretagogues are on the World Anti-Doping Agency's prohibited list.

Storage and handling

Keep capsules or powder sealed, dry and away from heat and light.

Key references

• 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.
• 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. Arch Gerontol Geriatr. 2011.
• Search PubMed for MK-677 studies

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