Additionally, the positive rates of elevated myostatin and reduced irisin were significantly higher in RA patients than in controls (myostatin: 59.9% vs. 25.4%, χ2 = 38.484, P < 0.001; irisin: 94.0% vs. 43.0%, χ2 = 1022.033, P < 0.0001) (Table 1). This evidence concerns the gene FNDC5 and rheumatoid arthritis.