In this thesis the relation between thyroid hormones and the coagulation system will be examined. As an introduction, the hypothalamic-pituitary-thyroid axis, the coagulation system and their... Show moreIn this thesis the relation between thyroid hormones and the coagulation system will be examined. As an introduction, the hypothalamic-pituitary-thyroid axis, the coagulation system and their interactions will be discussed. A short overview of the literature preceding the research reported in this thesis is about the relation between thyroid hormones, the coagulation system, and risk of bleeding and venous thrombosis. In conclusion, in the studies in this thesis we found strong evidence that higher than average levels of FT4 increase the risk of venous thrombosis. Weak evidence is provided that lower than average levels of FT4 give an increased risk of bleeding in patients using vitamin K antagonists. A hypothyroid state possesses probably both pro- and anti-coagulant properties. The effect of FT4 on venous thrombosis is mediated at least by coagulation factors factor VIII and von Willebrand factor. Show less
Venous thrombosis is a disease that occurs in 1-2 per 1000 people per year. At the time of their first venous thrombosis, approximately 50% of women are exposed to reproductive risk factors (oral... Show moreVenous thrombosis is a disease that occurs in 1-2 per 1000 people per year. At the time of their first venous thrombosis, approximately 50% of women are exposed to reproductive risk factors (oral contraception, postmenopausal hormone therapy, pregnancy and the puerperium). In this thesis, we showed that these women are at particularly high risk of venous thrombosis if they have previously experienced an episode of superficial vein thrombosis, or are over the age of 50 years (Chapters 2 and 3). There is no known male counterpart to female reproductive risk factors. Nevertheless, the incidence of venous thrombosis is approximately similar in men and women. In this thesis we established that, once female reproductive risk factors are taken into account, men have an approximately twofold higher risk of both first and recurrent venous thrombosis than women (Chapters 4 and 5). Further to these findings, in Chapter 6, we reviewed the literature on sex-specific risk factors for venous thrombosis. We hypothesized that sex-specific genetic risk factors, an excess in overweight and smoking, or hypercoagulable changes such as microalbuminuria may explain the higher risk of venous thrombosis in men than in women. Show less
