MK-677 (Ibutamoren)
FitnessAlso known as: Ibutamoren, Ibutamoren Mesylate, MK-0677, Nutrobal
Well-StudiedWhat is MK-677 (Ibutamoren)?
An orally active growth hormone secretagogue that mimics ghrelin, the hunger hormone. Despite being widely sold alongside peptides and SARMs, MK-677 is technically a non-peptide small molecule. It was studied extensively but never FDA-approved, and carries significant metabolic concerns.
How it works
Mimics ghrelin by binding to the growth hormone secretagogue receptor (GHSR) in the brain, stimulating the pituitary to release growth hormone. Unlike injectable peptides, it is orally bioavailable. Also increases IGF-1 levels and stimulates appetite through the same ghrelin pathway.
What marketers claim
- ▸oral alternative to growth hormone injections
- ▸builds muscle without exercise
- ▸safe because it is not a steroid
- ▸no significant side effects
What evidence supports
- ✓consistently raises GH and IGF-1 levels in clinical studies
- ✓oral bioavailability is a significant practical advantage over injectable peptides
- ✓two-year study showed sustained IGF-1 elevation without tachyphylaxis
- ✓may improve sleep quality and increase slow-wave sleep
- ✓increased lean mass in some elderly populations
Research evidence
Key studies on MK-677 (Ibutamoren), summarized in plain language. This is not an exhaustive list — it highlights the most relevant findings.
Two-year effects of MK-677 on GH, IGF-1, body composition, and function in healthy older adults
Finding: MK-677 sustained elevated GH and IGF-1 over 2 years and increased fat-free mass. However, there was no improvement in functional performance, strength, or body fat percentage. Fasting glucose increased significantly.
Limitation: Elderly population. The disconnect between hormonal changes and functional outcomes raises questions about clinical utility.
MK-677 stimulates GH secretion and improves sleep quality
Finding: MK-677 increased GH secretion by 97% and significantly increased stage IV (deep) sleep duration by 50% and REM sleep by 20%.
Limitation: Very small sample size. Sleep improvements may partly explain the subjective benefits reported by users.
Best for
What to expect
Realistic timeline based on available research. Individual results vary.
Day 1-3
Increased appetite is typically the first noticeable effect. Some users report improved sleep quality within the first few nights.
Week 1-2
Water retention and slight weight gain are common. IGF-1 levels begin rising measurably. Numbness or tingling in hands may occur.
Month 1-3
GH and IGF-1 levels reach elevated steady state. Some improvements in recovery and skin quality reported anecdotally. Appetite increase persists.
Month 6+
Long-term studies show sustained GH/IGF-1 elevation. However, the two-year trial in elderly showed no meaningful improvement in strength or function despite hormonal changes.
Safety notes & concerns
Full safety guide →- ⚠significantly increases appetite — can lead to unwanted weight gain
- ⚠raises fasting blood glucose and may reduce insulin sensitivity
- ⚠two-year study in elderly showed no improvement in functional outcomes despite increased GH/IGF-1
- ⚠may cause water retention, joint pain, and numbness/tingling
- ⚠long-term elevated IGF-1 is associated with increased cancer risk in epidemiological studies
- ⚠not FDA approved for any indication
- ⚠often sold through unregulated SARMs vendors with quality concerns
Pairs well with
Use caution with
Frequently asked questions
Is MK-677 a SARM?
No. MK-677 is a growth hormone secretagogue, not a selective androgen receptor modulator. It does not interact with androgen receptors. It is often sold alongside SARMs by the same vendors, which has created this common misconception.
Does MK-677 actually build muscle?
MK-677 raises GH and IGF-1 levels, which are involved in muscle growth. However, the largest clinical trial (2-year study in elderly) showed no significant improvement in strength or functional capacity despite sustained hormonal elevation. The muscle-building claims outpace the clinical evidence.
Why was MK-677 never approved?
Despite extensive clinical study, MK-677 failed to demonstrate sufficient clinical benefit relative to its side effects. The increases in blood glucose and insulin resistance were particularly concerning, and the two-year study showed elevated GH markers did not translate to meaningful functional improvements.
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Last updated: 2025-04-09
Medical Disclaimer
The information on this site is for educational and informational purposes only. It is not intended as medical advice and should not be used to diagnose, treat, or prevent any condition. Always consult with a qualified healthcare professional before starting any new supplement, peptide, or treatment protocol.