INS and breast carcinoma: In another causal mediation analysis of the adiposity–ER‐positive postmenopausal breast cancer association (RR for BMI>30 vs. ≤25 kg/m2 1.75; 95%CI, 1.05–2.91), conducted as a case–control study within the Melbourne Collaborative Cohort Study (MCCS), 72% of the effect was explained by free estradiol (RR 1.56; 95% CI, 1.11–2.19) and 28% by fasting insulin (RR 1.12; 95%CI, 0.68–1.84).45