MSTN and Duchenne muscular dystrophy: These were: (1) the distinct differences in native myostatin levels in mice compared to humans (by ~10 fold); (2) disparity in the proportional basal suppression of circulating myostatin between wild-type/healthy and mdx/DMD muscles (skeletal muscle myostatin is 25% of wild-type levels in mdx mice compared to 8% of healthy control levels in DMD patients); and (3) the confounding effects of standard of care corticosteroid treatment in DMD patients which was never extensively tested in pre-clinical animal trials.