Molecular data
| Molecular formula | C27H36N4O5S |
|---|---|
| Molecular weight | 528.66 Da |
| CAS / identifier | Ibutamoren (MK-677, L-163,191) |
| Physical form | Capsules (12.5 mg × 60) |
| Available sizes | 12.5mg |
How it works
Ghrelin Receptor Agonism
MK-677 (Ibutamoren) mimics the action of ghrelin, binding to and activating the growth hormone secretagogue receptor (GHSR) in the hypothalamus and pituitary to stimulate the release of growth hormone.
- Selective, orally active GHSR agonist
- Stimulates pulsatile GH release
- Does not significantly raise cortisol
GH & IGF-1 Elevation
By amplifying endogenous growth hormone secretion, MK-677 has been observed in clinical studies to raise circulating IGF-1 levels while preserving the natural pulsatile pattern of GH release.
- Increases GH and IGF-1 concentrations
- Preserves physiologic GH pulsatility
- Effects sustained with daily oral dosing
Body Composition & Sleep
Research has examined MK-677 for its effects on lean body mass, nitrogen balance, bone turnover markers, and sleep architecture across multiple study populations.
- Studied for lean mass and nitrogen retention
- Investigated for bone-turnover markers
- Reported effects on slow-wave sleep
What the research shows
GH / IGF-1 Axis
Sustained elevation of growth hormone and IGF-1 levels with once-daily oral administration observed in healthy adult study populations.
Chapman et al. 1996
Lean Mass & Bone
Investigated for increases in fat-free mass, nitrogen retention, and bone-turnover markers in studies of older adults and catabolic states.
Murphy et al. 1999
Frailty & Recovery
Examined in older adults for effects on muscle strength, functional capacity, and recovery following hip-fracture rehabilitation.
Adunsky et al. 2011
Sleep Architecture
Reported to increase stage IV (slow-wave) sleep and REM sleep duration in young and older subjects in controlled studies.
Copinschi et al. 1997
Specification
| Chemical Name | Ibutamoren (MK-677, L-163,191) |
|---|---|
| Molecular Weight | 528.66 g/mol |
| Molecular Formula | C₂₇H₃₆N₄O₅S |
| Form | Capsules (12.5 mg × 60) |
| Purity | ≥99% (HPLC verified) |
| Testing | Third-party HPLC, Mass Spectrometry |
| Storage | Cool, dry place away from direct light |
| Class | Non-peptide growth hormone secretagogue |
| Administration (research) | Oral |
| COA | Included with every order |
Frequently asked questions
What is MK-677 and how does it work?
MK-677 (Ibutamoren, also known as L-163,191) is an orally active, non-peptide growth hormone secretagogue. It mimics the hormone ghrelin by binding to and activating the growth hormone secretagogue receptor (GHSR), which stimulates the pituitary gland to release growth hormone (GH) and, in turn, increase IGF-1 levels.
Is MK-677 FDA approved?
No. MK-677 is not approved by the FDA or any regulatory agency for human use. It has been studied in clinical trials but was never brought to market as an approved therapeutic. It is classified as an unapproved drug and is sold here strictly for in vitro and laboratory research purposes.
What does the research show about MK-677?
Clinical and preclinical studies have examined MK-677 for its ability to increase GH and IGF-1 levels, support lean body mass and nitrogen retention, influence bone-turnover markers, and increase slow-wave and REM sleep. Some studies in older adults explored effects on muscle function and frailty. Findings vary by population and study design.
How is MK-677 used in research settings?
In research, MK-677 is administered orally. Clinical studies have typically used daily doses in the range of 10–25 mg. This product is supplied as 12.5 mg capsules for controlled research dosing. It should only be handled by qualified researchers in appropriate laboratory settings.
What are the reported side effects of MK-677?
Commonly reported effects in studies include increased appetite, mild fluid retention, transient lethargy, and reversible increases in fasting blood glucose and insulin. Long-term safety in humans has not been fully established, which is one reason it remains an unapproved compound.
How should MK-677 be stored?
Store MK-677 capsules in a cool, dry place away from direct light, heat, and moisture. Keep the container tightly sealed. Proper storage helps maintain compound stability and potency over time.
Literature
- PubMed Oral MK-677, a growth hormone secretagogue, increases GH and IGF-1 in healthy adults
- PubMed Effects of an oral ghrelin mimetic on body composition in healthy older adults
- PubMed Growth hormone secretagogue MK-677 and functional recovery after hip fracture
- PubMed Effects of growth hormone secretagogue MK-677 on sleep quality
For laboratory research use only. Not a drug, supplement, or medical product; not for human or animal use. All findings referenced are from published preclinical/laboratory research.