MK-677 (Ibutamoren)

MK-677 (Ibutamoren) is an orally bioavailable, non-peptide growth hormone secretagogue that mimics the action of ghrelin at the GHS-R1a receptor. While technically not a peptide, it is commonly grouped with peptide research compounds due to its mechanism of action and research applications in GH/IGF-1 studies.

Unlike injectable GH secretagogues, MK-677's oral bioavailability and extended half-life (approximately 24 hours) enable once-daily dosing with sustained receptor activation. Research has demonstrated it produces significant elevations in growth hormone, IGF-1, and IGFBP-3 levels while preserving the natural pulsatile pattern of GH secretion.

Long-term studies have shown MK-677 maintains its GH-releasing efficacy without significant tachyphylaxis, though IGF-1 levels may plateau over extended administration. The compound also increases appetite through ghrelin pathway activation, which may be beneficial or limiting depending on research objectives.

MK-677 has been investigated in clinical research for sarcopenia, growth hormone deficiency, and sleep disorders, with studies demonstrating improvements in lean body mass, sleep quality (particularly slow-wave sleep duration), and functional measures in elderly populations. Its oral route and sustained action make it valuable for studying chronic GH/IGF-1 axis modulation.