Myostatin

Full name: GDF-8

A member of the TGF-β superfamily that acts as a negative regulator of muscle growth. Naturally limits skeletal muscle hypertrophy. Follistatin (both FST-344 and FST-315 isoforms) inhibits myostatin by direct binding. Animals with myostatin knockouts or deficiencies display dramatic muscle overgrowth. A major target in research on muscle-wasting diseases and performance enhancement.