Hormonal Therapies and Venous Thrombosis

The association between hormone replacement therapy (HRT) and venous thromboembolism (VTE) was matter of discussion until ’90 years. Although an increased incidence of thrombotic events has been always described in population taking HRT, several reports did not find significant association between both conditions until 1996 [3, 4]. However, beginning from 1996 most and most Authors found a significant association between HRT and VTE in several types of clinical studies (i.e. observational studies, casecontrol studies, prospective and follow up studies) [5-7]. Moreover, the association between HRT and venous thrombosis was underlined in the first year both for deep vein thrombosis and pulmonary embolism if women ongoing HRT were compared to non-users [8]. Probably first studies failed to demonstrate this topic because a different design and different magnitude of studies; moreover, old studies frequently did not have objective diagnostic methods for VTE [8]. Most studies showed that thrombotic risk is highest in the first year of use of HRT, while other studies showed that thrombotic risk persists also in following years [9]. From a pharmacological point of view there are no difference between the administration of HRT (i.e. transdermal or per os) nor for single oestradiol administration or for combined hormonal therapies [10].