MK-677 (Ibutamoren)

In this 2-year double-blind, placebo-controlled, modified-crossover trial in 65 healthy adults aged 60-81, oral MK-677 25 mg daily increased pulsatile GH secretion and raised IGF-1 into the range seen in young adults, and significantly increased fat-free mass (approximately 1.1 kg at 12 months versus placebo). However, there was no accompanying improvement in muscle strength, physical function, or quality of life, and the gain was in lean mass rather than fat loss. Notably, MK-677 produced a mild increase in fasting blood glucose and insulin resistance and a small rise in HbA1c, alongside increased appetite and transient edema.

Taking MK-677 as a daily pill for a year raised growth hormone and IGF-1 levels and added a little over a kilogram of lean (non-fat) body mass in healthy older adults. But it did not make people measurably stronger, more physically capable, or improve their quality of life. It also nudged blood sugar and insulin resistance in the wrong direction and caused increased appetite and some fluid retention, so the modest body-composition change came with real metabolic trade-offs.

This multicenter randomized, placebo-controlled phase IIb trial gave 123 elderly hip-fracture patients MK-0677 25 mg/day (n=62) or placebo (n=61) during recovery. MK-0677 raised plasma IGF-1 by about 51 ng/mL versus placebo and modestly improved gait speed, but most functional performance measures did not improve, so the biochemical effect did not translate into broad functional recovery. Critically, the trial was terminated early for a safety signal: congestive heart failure occurred in 4 of 62 MK-0677 patients (6.5%) versus 1 of 61 (1.7%) on placebo, and the authors concluded the drug had an unfavorable safety profile in this frail population.

Researchers tested whether MK-677 could help elderly patients recover after a broken hip. Although it raised IGF-1 levels and slightly improved walking speed, it did not improve most measures of physical recovery. The study was stopped early because more patients on the drug developed heart failure than those on placebo, and the researchers concluded it was not safe enough for this vulnerable group.

In this randomized, double-blind, placebo-controlled study, 32 healthy subjects aged 64-81 received placebo or 2, 10, or 25 mg oral MK-677 daily across dosing periods of 14 and 28 days. Once-daily MK-677 enhanced pulsatile GH release and significantly increased serum GH and IGF-1, with the 25 mg dose restoring IGF-1 concentrations to those typical of young adults. This early trial established the pharmacodynamic effect on the GH/IGF-1 axis over weeks but was short-term and not designed to assess body composition, functional outcomes, or long-term metabolic safety.

This foundational study showed that a daily MK-677 pill could reliably boost growth hormone and IGF-1 in healthy older people, with the 25 mg dose bringing IGF-1 back up to youthful levels within a few weeks. It proved the drug works on the hormone system as intended. However, it was a short study measuring hormones only, so it does not tell us whether those hormone changes produce real benefits or are safe over the long term.