MSTN and rheumatoid arthritis: Compared with healthy controls, RA patients showed a higher level of serum myostatin at baseline (3.241 ± 1.679 ng/ml vs. 1.717 ± 0.872 ng/ml, Figure 1A), although lower ASMI (6.0 ± 0.9 kg/m2vs. 6.5 ± 1.0 kg/m2, both P<0.001, Table 1).