Hormone replacement therapy and risk for venous thromboembolism: what's new and how do these findings influence...

Although an association between hormone replacement therapy and venous thromboembolism has been established, several unanswered questions remain. This review will address additional questions relating to hormone replacement therapy and venous thromboembolism. Does the risk for venous thromboembolism differ according to the type of hormone replacement therapy? Does the presence of thrombophilia influence the risk for venous thromboembolism in hormone replacement therapy users? Should hormone replacement therapy be temporarily interrupted around the time of surgery?

The risk for venous thromboembolism seems to be less in users of estrogen-only hormone replacement therapy (odds ratio = 1.2; 95% confidence interval: 0.6-2.6) than in users of estrogen-progestin hormone replacement therapy (odds ratio = 2.7; 95% confidence interval: 1.4-5.1), and there may be no increased risk for venous thromboembolism with transdermal hormone replacement therapy (odds ratio = 1.0; 95% confidence interval: 0.3-3.3). The presence of a prothrombotic blood abnormality, such as the factor V Leiden mutation, seems to further increase the risk for venous thromboembolism in hormone replacement therapy users (odds ratio = 17.1; 95% confidence interval: 3.7-78). Continued use of hormone replacement therapy in the perioperative period does not seem to have an impact on the overall risk for postoperative venous thromboembolism (odds ratio = 0.66; 95% confidence interval: 0.35-1.18).

Recent studies have extended our understanding regarding the association between hormone replacement therapy and venous thromboembolism. The implications of these findings on clinical practice are discussed.