Myostatin (MSTN, or GDF8) is a member of the transforming growth factor beta (TGF-β) superfamily and may prove to be a promising biologically relevant marker, in part from its role as an autocrine inhibitor of muscle growth, contributing to muscle wasting in patients with sarcopenia, which are major issues in cirrhosis and HCC. The gene discussed is MSTN; the disease is sarcopenia.