The present relates to use of follistatin-like related gene (FLRG) to increase muscle mass in a subject. As such, methods of ameliorating the severity of a pathologic condition characterized, at least in part, by a decreased amount, development or metabolic activity of muscle are provided. In addition transgenic non-human mammals expressing FLRG and having increased muscle mass as compared to a corresponding mammal having a myostatin-null mutation or a decreased level of myostatin are provided.