Association of genetically predicted serum estradiol with risk of thromboembolism in men: A mendelian randomization study
Abstract Context An association was recently reported between genetic markers related to high testosterone and increased risk of thromboembolism in men but a possible causal role of estradiol for risk of thromboembolism in men remains unknown. Objective To determine whether endogenous estradiol has a causal role in thromboembolism in men. Design Two-sample mendelian randomization study using gene-based genetic instruments Setting UK Biobank Participants We assessed the association between endogenous estradiol genetically predicted by 22 variants in the CYP19A1 gene region and risk of thromboembolism (5815 cases) in 170,593 unrelated men of white ancestry in the UK Biobank. Main Outcome Measure Thromboembolism based on self-reports, hospital episodes, and death. Results Endogenous estradiol genetically predicted by variants in the CYP19A1 gene region was inversely associated with risk of thromboembolism (odds ratio per SD increase in estradiol 0.74, 95% confidence interval 0.62-0.90). In contrast, genetic variants in the JMJD1C gene, used as a predictor of high endogenous testosterone, were associated with an increased risk of thromboembolism (odds ratio per SD increase in testosterone 1.39, 1.12-1.72). Subsequent explorative analyses evaluating potential repercussions of thromboembolism revealed that endogenous estradiol genetically predicted by variants in the CYP19A1 gene region was inversely associated with risk of ischemic stroke (0.68, 0.49-0.95) but not myocardial infarction (0.97, 0.84-1.13). Conclusions Genetically predicted estradiol was inversely associated with risk of thromboembolism and ischemic stroke in men. The ratio between testosterone and estradiol, determined by aromatase (CYP19A1) activity, may contribute to the overall impact of sex steroids on thromboembolism in men.