Postmenopausal hormone therapy (HT), which consists of exogenous estrogens with or without combined progestogens, remains the most effective treatment of climacteric symptoms. Depending on its characteristics, it may nevertheless increase the risk of venous thromboembolism, and its effects on hemostasis have been studied for several decades. The aim of this review was to summarize current knowledge on the effects of HT on hemostasis, taking into account the route of estrogen administration, the daily dose and chemical structure of estrogens, and the pharmacologic class of progestogens.
Data from randomized controlled trials that included a control group (either placebo or no treatment) were selected, and analysis was conducted on different generations of biomarkers.
Overall, studies showed a hemostasis imbalance among oral estrogen users with a decrease in coagulation inhibitors and an increase in markers of activation coagulation, leading to global enhanced thrombin generation. By contrast, transdermal estrogen use was associated with less change in hemostasis variables and did not activate coagulation and fibrinolysis. No clear difference in HT effects on hemostasis was highlighted between daily doses of estrogens, between estrogen compounds, and between pharmacologic classes of progestogens.
Changes in hemostasis are in accordance with clinical results showing an increased thrombotic risk with oral—but not transdermal—estrogen use.