TNFSF11 and rheumatoid arthritis: Pooled results of five studies [23,33,37,38,42] including 376 patients with RA showed that IGU was associated with increased serum OPG (MD: 180.36 pg/ml, 95% CI: 122.52 to 238.20, p < 0.001, I2 = 48%; Figure 2(b)) and decreased serum RANKL (MD: −10.65 pmol/l, 95% CI: −15.59 to −5.72, p < 0.001, I2 = 53%; Figure 2(c)).