Myostine, scientifically designated YK-11, is a synthetic compound with a dual mechanism of action: it functions simultaneously as a partial agonist of the androgen receptor and as an inhibitor of the growth factor myostatin (GDF-8), which mechanistically distinguishes it from all other known SARMs.
Dual Mechanism of Action: AR Agonism and Myostatin Inhibition
Myostatin is an endogenous protein belonging to the TGF-β superfamily that acts as a negative regulator of skeletal muscle mass. In cell culture experiments, YK-11 inhibits the myostatin signaling cascade by stimulating the expression of follistatin — a natural myostatin antagonist. Concurrently, YK-11 binds to the androgen receptor with measurable affinity and induces partial activation without adopting the full agonist conformation. This dual mechanism is unique within SARM research and fundamentally distinguishes YK-11 from compounds such as Ostarine or LGD-4033, which act exclusively through the AR. All data published to date derive from cell culture studies; controlled animal studies and human clinical data are largely absent.
Chemical Structure and Distinction from Steroid Chemistry
Structurally, YK-11 features a steroidal scaffold, setting it apart from most SARMs, which are built on non-steroidal frameworks. Despite this structural resemblance to steroids, YK-11 is not classified as a classical steroid, as key functional groups are absent or modified. This intermediate status makes YK-11 a pharmacologically complex subject of research. Its metabolic profile and safety characteristics have not been systematically characterized in humans; potential hepatotoxic effects are referenced in scientific discussion, though they remain unsubstantiated by controlled studies.
Range & Selection
The range includes two formulations for research applications:
Myostine | 5 mg/Tab | 30 Tablets | Vital Research – Oral tablet formulation with precisely dosed YK-11 content; enables reproducible experimental approaches in cell culture and laboratory research.
YK-11 (Myostine) | 4 mg/Vial | 1 Vial | Master Pharma – Injectable formulation containing 4 mg of active compound per vial; suitable for research applications where a parenteral route of administration is methodologically required.
Lab Tested