What is MK-677 (Ibutamoren) and how does it affect growth hormone levels?

MK-677 (Ibutamoren) is an oral growth hormone secretagogue that mimics ghrelin to stimulate GH release from the pituitary gland. Research shows it can increase mean 24-hour GH concentrations by up to 97% and IGF-1 levels by 55-88% over several weeks. Studies have demonstrated modest increases in fat-free mass, though it may also raise fasting glucose and reduce insulin sensitivity.