MK-677
Also known as · Ibutamoren · L-163,191
Overview
An orally bioavailable, non-peptide ghrelin-receptor agonist that raises GH and IGF-1 for 24 hours per dose. Widely studied but never approved; included here for completeness of the secretagogue class.
Research profile · for clinicians
Based on research: the most thoroughly studied oral secretagogue, with multi-year human trials in older adults and in hip-fracture recovery. Consistent IGF-1 elevation with lean-mass gain.
Mechanism of action
Mimics ghrelin at GHS-R1a with oral bioavailability and a long duration, producing sustained amplification of endogenous GH pulses and downstream hepatic IGF-1 output.
Research record
- [01]Two-year trial in healthy older adults: sustained IGF-1 increase and lean-mass gain (Nass et al., 2008).
- [02]Reported effects include increased appetite, water retention, and reduced insulin sensitivity.
Selected references
Effects of an oral ghrelin mimetic on body composition in healthy older adults
Ann. Intern. Med., 2008
Research deep dive
Every cited study, explained
Plain-language walkthroughs of each reference, with direct PubMed links and dosing-literature context.