FGF23 and breast cancer: Utilizing independent SNPs as IVs, our IVW-MR analysis revealed that individuals genetically predisposed to ER+ BC are likely to have increased levels of FGF7 (OR 1.072, 95% CI: 1.004–1.144, P = .037) and FGF23 (OR 1.071, 95% CI: 1.005–1.142, P = .036), and decreased levels of FGFR2 (OR 0.930, 95% CI: 0.872–0.992, P = .027; Fig. 5).