MK-677 (Ibutamoren)

What is MK-677 (ibutamoren)?

MK-677, also called ibutamoren, is worth one clarification up front: it is not a peptide. It is a small, orally active molecule that mimics ghrelin, and it is grouped here because it does the same job as the injectable GH secretagogues, raising your own growth hormone, just in a daily pill instead of a shot. It is not FDA-approved, but unlike most of this list it has a real human trial history, and that history includes some safety signals worth taking seriously.

How MK-677 (ibutamoren) works

MK-677 activates the ghrelin receptor (the growth-hormone secretagogue receptor) in the brain and pituitary, telling the pituitary to keep releasing growth hormone, which in turn raises IGF-1. Because it is orally absorbed and long-acting, a single daily dose produces a sustained lift in GH and IGF-1 rather than a brief pulse. That convenience, no injections, is a big part of its popularity, but the sustained elevation is also where some of its downsides come from.

What the research shows

There is genuine human data here. A single daily oral dose has been shown to raise 24-hour growth-hormone secretion substantially in older adults, and multiple trials document sustained IGF-1 increases of roughly 40 to 70% over weeks of use. In other words, it reliably does what it claims to the hormones. The catch is that "raises GH and IGF-1" is not the same as "safe and beneficial long-term," and the trial record includes some concerning signals, covered below.

Dosage and how it is used

Clinical trials generally used 25 mg once daily, taken orally. The community has largely drifted lower, often to around 10 to 12.5 mg, in part to limit side effects like water retention and appetite. Because it is oral and long-acting, timing is flexible, though some people dose at night given its effects on sleep and hunger.

→ MK-677 dosing reference: how it is taken, timing & considerations

Side effects and safety

This is the part that deserves attention. MK-677 raises fasting blood glucose and reduces insulin sensitivity, and studies have shown increases in HbA1c, so it can push metabolism in a diabetic direction. It commonly causes water retention, increased appetite, and joint or hand stiffness. Most importantly, a trial in older adults was stopped early over concern that MK-677 may have contributed to congestive heart failure in people without prior heart failure, and increases in blood pressure have been reported. Long-term safety has not been established, and these signals should not be waved away.

• Research depth: real human trials, but with documented negative safety signals.
• Raises blood glucose and HbA1c; a cardiac-failure signal appeared in an older-adult trial.
• Oral, not a peptide, not FDA-approved. Verify current legal and regulatory status independently.

Frequently asked questions

References

• Nass R et al. Effects of an oral ghrelin mimetic (MK-677) on body composition in healthy older adults. Annals of Internal Medicine, 2008.
• MK-677 (Ibutamoren): performance and safety overview. Operation Supplement Safety (US DoD).