MK-677 is a non-peptide agonist of the ghrelin receptor (GHSR-1a). Binds with high affinity (Ki ~0.5 nM) to mimic ghrelin’s stimulation of GH release from the pituitary without degradation by serum proteases. Increases amplitude and frequency of GH pulses while elevating IGF-1 levels. Unlike GHRH analogs, active orally.
Also Known As
Ibutamoren, MK-0677, L-163,191
Compound Class
Oral GHSR-1a agonist / GH secretagogue
Molecular Formula
C₂₇H₃₆N₄O₅S
Molecular Weight
528.66 Da
CAS Number
159752-10-0
Half-Life
~24 hours (once-daily oral dosing)
Research Applications
GH Deficiency / IGF-1 Restoration
Studies in GH-deficient adults show MK-677 significantly raises serum GH and IGF-1 to youthful ranges. Maintains GH pulsatility vs continuous infusion. Coadministration with GHRH analogs produces additive effects.
Muscle Mass & Body Composition
Phase 2 RCT in healthy elderly (N=65, 2 years): MK-677 increased lean body mass (+1.6 kg vs placebo, p<0.05) and bone mineral density. Associated with increased protein turnover markers. DIO rodent models: preserved lean mass during caloric restriction.
Sleep Architecture
MK-677 increases slow-wave sleep (SWS) duration via GHSR-1a in hypothalamic sleep regulation centres. Phase 1/2 crossover study in young and elderly volunteers: significant SWS increase, REM improvement.
Bone Density Research
GHSR-1a activation stimulates osteoblast activity and suppresses bone resorption. Phase 2 in hip fracture patients showed reductions in bone resorption markers. Relevant model for osteoporosis research.
Cognitive / Nootropic Research
GHSR-1a receptors in hippocampus and cortex. GH/IGF-1 axis linked to synaptic plasticity, neurogenesis. Rodent studies: improved spatial memory in aged mice. Emerging research interest in neurodegeneration.
Key Research Data
Study / Source
Key Findings
Svensson et al. 1998 JCEM
Single-dose MK-677 in healthy men: dose-dependent GH release, 24-hour IGF-1 elevation, no suppression of pituitary response
Murphy et al. 1998 J Endocrinol
2-year RCT in elderly: lean mass +1.6 kg, fat mass neutral, GH/IGF-1 normalised
Copinschi et al. 1997 Sleep
Crossover study: MK-677 increased SWS by 50% vs placebo, no effect on REM latency
Adunsky et al. 2011 JAMDA
Hip fracture trial: MK-677 vs placebo — muscle strength, functional improvement trends, reduced bone resorption markers
Specifications
Format
Oral tablet — 10mg per tablet
Purity
≥99% HPLC
Identity
MS confirmed
Storage
Room temperature, away from moisture
Reconstitution
N/A — oral administration
Frequently Asked Questions
What is MK-677 (Ibutamoren)?
MK-677 (Ibutamoren) is an oral GHSR-1a agonist that mimics ghrelin to stimulate GH release from the pituitary. Unlike peptide GH secretagogues, it is orally active with a ~24-hour half-life. Used in research models studying GH deficiency, muscle wasting, bone density, and sleep architecture.
How does MK-677 differ from peptide GH secretagogues like Ipamorelin or GHRP-2?
MK-677 is a non-peptide small molecule that survives oral administration and serum proteases. Ipamorelin, GHRP-2, and similar GH secretagogues are peptides requiring injection and have shorter half-lives (1-3 hours). MK-677 produces a more sustained GH elevation over 24 hours vs the acute pulse from injectable secretagogues.
Does MK-677 raise IGF-1 as well as GH?
Yes — GH elevation from MK-677 drives hepatic IGF-1 synthesis. Phase 2 RCT data show IGF-1 levels increase proportionally with GH and remain elevated throughout treatment. This is the primary mechanism for the lean mass and bone density effects observed in research models.
Does QSC ship MK-677 to the USA?
Yes. QSC MK-677 is available with domestic USA shipping and ships to EU, UK, Canada, and Australia. All batches carry Janoshik third-party COA confirming ≥99% HPLC purity and MS identity verification.
