MSTN and Duchenne muscular dystrophy: Concerning GDF8, in the most atrophic (SMA) and most wasting (DMD) muscle diseases studied a two-fold or higher decrease of circulating GDF8 was observed (SMA 30.6% ± 13.7 and DMD 50.6% ± 17.18 GDF8 compared with controls, respectively) (Fig. 1c).