MSTN and rheumatoid arthritis: Additionally, serum myostatin levels presented a direct correlation with the duration of RA (13 (0–45) years of duration) (r = 0.24, p = 0.02), with C-reactive protein (CRP) (r = 0.40, p < 0.001), with the erythrocyte sedimentation rate (ESR) (r = 0.28, p = 0.009), as well as with the total dose of glucocorticoids (r = 0.51, p < 0.001) [61].