The effects of an extremely high dose of levothyroxine on coagulation and fibrinolysis.

Several haemostatic abnormalities have been reported in thyroid hormone excess. However, the overall effect on coagulation and fibrinolysis is still unclear. We were presented the unique opportunity to further explore the effects of excessive levels of thyroid hormone in the case of a young woman who attempted suicide by auto-intoxication with levothyroxine. Levels of thyroid hormones and parameters of coagulation and fibrinolysis were assessed in the days following the autointoxication. We found a marked increase in levels of coagulation factors VIII, IX and X, von Willebrand factor and plasminogen activator inhibitor-1, resulting in enhanced thrombin generation after intoxication with 25 mg of levothyroxine. These findings suggest that thyroid hormone excess shifts the haemostatic balance towards a hypercoagulable and hypofibrinolytic state, and is therefore likely to reflect an increased risk of venous thrombosis. 154 Levothyroxine auto-intoxication