YK-11
Muscle Growth & Body CompositionAlso known as: YK11, Myostine
Mechanism
YK-11 is a unique steroidal compound that acts as both a partial androgen receptor agonist and a myostatin inhibitor. By simultaneously activating AR in muscle tissue and inhibiting myostatin (the protein that limits muscle growth), it has a dual mechanism for promoting muscle hypertrophy. Its steroidal backbone and dual action make it distinct from classical non-steroidal SARMs.
Technical detail
YK-11 is a steroidal compound structurally related to 5α-dihydrotestosterone that functions as a partial AR agonist with the unique additional property of inducing follistatin expression, thereby inhibiting myostatin signaling through the ActRIIB-Smad2/3 pathway. In C2C12 myoblast studies, it upregulates follistatin mRNA and protein expression more potently than DHT. Its partial AR agonism combined with myostatin inhibition creates a dual anabolic mechanism. However, its steroidal structure means it may carry hepatotoxicity risk and endocrine suppression similar to oral anabolic steroids.