IGF1 and breast cancer: Genetically predicted each 1-SD higher risk of IGF-1 was associated with a 7.7% increased risk of BC [IVW-multiplicative random effects: OR 1.077 (95% CI: 1.029–1.128), p = 0.002], a 6.8% increased risk of ER + BC [IVW-multiplicative random effects: OR 1.068 (95% CI: 1.016–1.122), p = 0.009], and a 6.5% increased risk of ER- BC [IVW-multiplicative random effects: OR 1.065 (95% CI: 1.000–1.134), p = 0.049].