YK-11
Also known as: Myostine · SARM YK-11
A steroidal SARM that acts as both an androgen receptor partial agonist and a myostatin inhibitor, providing a dual mechanism for muscle growth.
Overview
YK-11 is a unique compound classified as a selective androgen receptor modulator (SARM) that also functions as a myostatin inhibitor — making it the only known compound with this dual mechanism. Structurally, YK-11 is a steroidal compound derived from DHT (dihydrotestosterone) that acts as a partial agonist of the androgen receptor. More importantly, YK-11 has been shown to increase follistatin expression in muscle cells, which in turn inhibits myostatin — the body's primary brake on muscle growth. This dual action of androgen receptor activation plus myostatin inhibition creates a powerful anabolic environment for muscle growth.
In cell studies, YK-11 induced more follistatin expression than DHT, suggesting superior muscle-building potential. It is popular in the performance enhancement community for its ability to promote lean muscle gains with potentially fewer androgenic side effects than traditional anabolic steroids.
Mechanism of Action
Partial agonist of the androgen receptor (AR), activating anabolic gene expression in muscle tissue. Simultaneously increases follistatin expression, which binds to and inhibits myostatin and activin A, removing the negative regulation of muscle growth. The dual AR agonism + myostatin inhibition provides synergistic anabolic effects.
Key Benefits
Potential Side Effects
Common Stacks
This peptide is commonly combined with the following compounds for synergistic effects:
Known Interactions
The following interactions have been documented for YK-11. Always consult a healthcare professional before combining compounds.
Use Caution (1)
Both have anabolic effects and potential liver impact. YK-11 is a myostatin inhibitor with steroidal structure, and oxandrolone is a 17-alpha alkylated steroid. Monitor liver enzymes.
Synergistic (1)
Both inhibit myostatin through different mechanisms. Follistatin binds and neutralizes myostatin directly while YK-11 increases follistatin production. Powerful muscle growth stack.
Scientific References
Quick Reference
Typical Dose
5-20mg (oral) or 10-20mg (injectable)
Frequency
1x daily (oral) or 2x daily (injectable)
Route
Oral or subcutaneous injection
Half-Life
~6-10 hours
Cycle Length
4-8 weeks, followed by 4-8 weeks recovery with PCT
FDA Status
Research compound — not FDA approved. Not approved for human use. Banned by WADA.
Need to calculate dosing?
Use our reconstitution calculator to determine exact syringe measurements.
Open CalculatorThis information is for educational purposes only. Consult a qualified healthcare professional before using any peptide. Dosing information reflects commonly reported protocols and may not be appropriate for everyone.
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