Mechanisms of hormonal therapy related thrombosis.

There is now compelling evidence that use of oral contraceptives and postmenopausal hormonal therapies containing various estrogens is associated with a weak, but clinically relevant risk of both arterial and venous thrombosis. The increased risk is related to type and dose of both estrogen and combined progestagen and mode of delivery. Treatment induces mainly subtle changes in individual components of the coagulation and fibrinolytic systems, but the overall effect is the induction of a prothrombotic phenotype. This brief review summarizes some of the mechanisms responsible the prothrombotic effects of such treatment.