MK-677 (Ibutamoren)

Also known as: Ibutamoren, MK-0677, L-163,191

MK-677 (Ibutamoren) is an orally active, non-peptide ghrelin receptor agonist that mimics the action of ghrelin on the growth hormone secretagogue receptor (GHSR). By binding to this receptor in the pituitary and hypothalamus, it stimulates the pulsatile release of growth hormone (GH), leading to a sustained elevation of insulin-like growth factor 1 (IGF-1) levels for up to 24 hours per dose. Unlike exogenous GH administration, MK-677 preserves the natural feedback regulation of the GH/IGF-1 axis, though it does not significantly increase cortisol or prolactin levels in most studies. Key research findings from clinical trials indicate that MK-677 can increase lean body mass, improve bone mineral density, and enhance muscle strength in elderly or growth hormone-deficient populations. Studies have also shown improvements in sleep quality and a reduction in visceral adiposity. However, transient increases in fasting glucose and insulin resistance have been observed, particularly in older or metabolically compromised individuals, suggesting a potential risk for glucose intolerance with long-term use. Clinically, MK-677 has been investigated for conditions such as frailty, sarcopenia, and growth hormone deficiency, though it has not received FDA approval for any indication. Its ability to elevate GH and IGF-1 without injection offers a practical advantage over traditional GH therapy, but the metabolic side effects and lack of long-term safety data limit its clinical adoption. Further research is needed to clarify its risk-benefit profile in specific patient populations. For research purposes only — not medical advice.

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