Synonyms: GDF-8, MSTN, growth differentiation factor 8, growth/differentiation factor 8 Myostatin is a member of the transforming growth factor beta (TGFBs) superfamily and the bone morphogenetic protein (BMPs) family. This protein is essential for proper regulation of skeletal muscle mass (it controls myoblast proliferation). Myostatin is a secreted protein that negatively regulates skeletal muscle mass determining both muscle fiber number and size (Rebbapragada et al., 2003). Studies have shown that Myostatin could play an important role in cardiac development and physiology. Genetic deletion of Myostatin or in vivo administration of the Myostatin propeptide induces muscle hypertrophy as well as enhanced glucose utilization and insulin sensitivity and a reduction in overall fat mass (Matsakas et al., 2009, Guo et al., 2009). Myostatin is a homodimeric prepropeptide that is cleaved by proprotein convertases such as furin to generate the dimeric N- terminal propeptide and the dimeric C-terminal mature active protein. The myostatin pathway is conserved and regulates muscle mass in a number of animal species ranging from fish to humans. Myostatin belongs to the transforming growth factor beta (TGFBs) superfamily, which includes : TGF betas, the bone morphogenetic protein (BMPs), growth differentiation factors (GDFs), activins and inhibins. As other members of this superfamily , is synthesized and secreted as a homodimeric prepropeptide that is cleaved by proprotein convertases such as furin to generate the dimeric N- terminal propeptide and the dimeric C-terminal mature active protein. Myostatin is one of the most important protein that controls myoblast proliferation and it is a potent negative regulator of skeletal muscle mass in a number of animal species. Several studies have shown that Myostatin could play an important role in cardiac development and physiology. Genetic deletion of Myostatin or in vivo administration of the Myostatin propeptide induces muscle hypertrophy as well as enhanced glucose utilization and insulin sensitivity and a reduction in overall fat mass.