IGF1 and Familial prostate cancer: Finally, if rs700752 is employed as an IV for serum IGF‐I and IGFBP‐3, based on ProtecT findings, the causal estimates regarding prostate cancer‐specific mortality were HR 0.72 (95% CI: 0.53, 0.98) per SD increase in IGF‐I, and HR 0.76 (95% CI: 0.60, 0.95) per SD increase in IGFBP‐3.