Identifying Women at High Risk of Venous Thrombosis before Administration of Hormone Therapy

Abstract

Over 100 million women worldwide use hormone therapy (HT), that is, oral contraceptives (OCs) or hormone replacement therapy (HRT); however, the use of HT is associated with an increased risk of venous thromboembolism (VTE), including deep-vein thrombosis, pulmonary embolism and cerebral vein thrombosis [1–3]. While the risk is low in absolute terms, OCs are the major cause of thrombotic events in young women [1]. The increased risk of VTE is most probably due to the administration of exogenous estrogens, which leads to procoagulant changes [1,2]. The risk is still present with low-dose OCs (second and third generations; 20–30 mg of the estrogen ethinylestradiol) used currently, and with HRT preparations, which contain even lower dosages of estrogen and progestin compared with OC. HRT increases the risk of VTE by 2–3-fold compared with women without HT [4]. The risk is higher during the first year of HT use (up to 1/1000/year), with the use of a third-generation OC (desogestrel or gestodene instead of levonorgestrel or norgestrel) and among women with thrombophilic risk factors [1].