CYP19A1 and endometrial cancer: Using a Mendelian randomization argument with CYP19A1 genotype as the instrumental variable, we have shown that the endometrial cancer OR per A-allele of rs727479 predicted on the basis of the per-allele effect on E2 (1.09, CI=1.03–1.21) is in line with the directly observed effect of each A allele on endometrial cancer (OR=1.15, CI=1.11–1.21) (Fig. 4).