Ibutamoren
Ibutamoren (MK-677)
Ibutamoren (MK-677) is a non-peptide, orally active growth hormone secretagogue that mimics the action of ghrelin, stimulating the pituitary gland to release growth hormone (GH) and subsequently increasing IGF-1 levels. It is primarily used in research contexts for its potential to promote muscle growth, improve body composition, enhance recovery, and support bone density. Unlike injectable GH or peptides, MK-677 is orally bioavailable and maintains elevated GH pulses over a 24-hour period with once-daily dosing.
Mechanism of Action
MK-677 acts as a potent, selective agonist of the ghrelin receptor (GHSR-1a), stimulating pulsatile GH secretion from the anterior pituitary without suppressing the body's own GH feedback mechanisms. This leads to downstream increases in hepatic IGF-1 production, which mediates many of its anabolic and regenerative effects. Unlike exogenous GH administration, MK-677 preserves the natural pulsatile pattern of GH release, which is considered more physiologically favorable.
Evidence by Health Goal(14 goals)
Dosing Protocols
30 minutes before bed to align GH pulse with natural nocturnal peak and minimize daytime hunger/lethargy side effects
Cycle: 12-16 weeks on, 4-8 weeks off; some protocols run continuously for 6+ months at lower doses
Beginners should start at 10mg to assess hunger and water retention response. The 25mg dose produces significantly greater GH/IGF-1 elevation but with more pronounced side effects. Some users split dosing (morning/evening) to blunt hunger spikes, though once-nightly is most common.
Safety & Side Effects
MK-677 has a relatively well-characterized short-term safety profile from clinical trials, with most adverse effects being dose-dependent and reversible upon discontinuation; however, long-term safety data beyond 2 years is limited, and its effects on insulin sensitivity warrant monitoring of fasting glucose in metabolically at-risk individuals. It is not FDA-approved for human use, is sold as a research chemical, and is banned by WADA; it is also not classified as a scheduled controlled substance in the US but faces regulatory restrictions in several countries.
Possible Side Effects
- !Significantly increased appetite and hunger, often pronounced and persistent
- !Water retention and mild edema, particularly in extremities and face
- !Lethargy and fatigue, especially during the first 2-4 weeks of use
- !Elevated fasting blood glucose and transient insulin resistance
- !Tingling or numbness in hands and fingers (carpal tunnel-like symptoms)
- !Elevated prolactin levels in some users, potentially causing mild gynecomastia
- !Joint discomfort or aching at higher doses due to fluid shifts
- !Vivid or intense dreams due to increased GH activity during sleep
Interactions
- -May worsen insulin resistance - use caution alongside diabetes medications such as metformin or insulin, as glucose-lowering dose adjustments may be needed
- -May amplify effects of exogenous growth hormone or IGF-1 preparations, risking excessive GH-related side effects
- -Can increase cortisol levels transiently - may blunt therapeutic effects of corticosteroids or interfere with HPA axis-related treatments
- -Potential additive fluid retention when combined with SARMs, anabolic steroids, or high-sodium diets - increases risk of edema
- -Ghrelin receptor activity may interact with medications affecting appetite regulation (e.g., GLP-1 agonists like semaglutide), potentially opposing satiety effects
Cost & Where to Buy
MK-677 is widely available from research chemical vendors at relatively low cost; 30mg/day dosing costs more than 10-15mg/day protocols. Price varies significantly by source purity and third-party testing quality. Pharmaceutical-grade or heavily tested products command premium pricing.
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