title: Prothrombotic changes due to an increase in thyroid hormone levels.
abstract: OBJECTIVE
  With increasing free thyroxine levels, a gradually rising risk of venous thromboembolism has been described in case-control studies. However, reports on the influence of thyroid hormones on haemostasis, while suggesting a hypercoagulable state in thyrotoxicosis, have often been inconclusive. This study evaluates multiple markers of haemostasis and fibrinolysis in a paired design, making it more sensitive to changes in thyroid hormone levels.
  
  
  METHODS
  We analysed multiple variables in patients who shifted from severe hypothyroidism to mild hyperthyroidism during thyroid cancer treatment. Those with possible residual disease were excluded.
  
  
  METHODS
  Ninety patients following total thyroidectomy were tested on two occasions: i) before radioiodine remnant ablation and ii) 6 weeks later, on levothyroxine (lT4) suppression treatment, and the results were compared using the Wilcoxon's test for paired data.
  
  
  RESULTS
  During lT4 treatment, significant increases (all P<0.001) in fibrinogen (from median 3.4 to 3.8 g/l), von Willebrand factor (from 85 to 127%), factor VIII (from 111 to 148%) and plasminogen activator inhibitor 1 (from 6.5 to 13.9 μg/l) were observed. In addition, the activation times of platelet adhesion and aggregation stimulated with collagen and epinephrine (EPI)/ADP, i.e. closure times in platelet function analyser (PFA-100), were significantly shortened (P<0.001): for EPI from median 148 to 117 s and for ADP from 95 to 80 s. Changes in other tests were less prominent or insignificant.
  
  
  CONCLUSIONS
  An increase in thyroid hormone levels shifts the haemostatic balance towards a hypercoagulable, hypofibrinolytic state. This may contribute to the increased cardiovascular morbidity and mortality observed even in mild thyrotoxicosis.
authors: 4 Department of Internal Medicine - HaematologyDepartment of Nuclear MedicineCharles University in Prague, Faculty of Medicine and University Hospital Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic jiri.horacek@fnhk.cz.
authors: Jiri
authors: J
authors: Horacek
authors: 4 Department of Internal Medicine - HaematologyDepartment of Nuclear MedicineCharles University in Prague, Faculty of Medicine and University Hospital Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic.
authors: Jaroslav
authors: J
authors: Maly
authors: 4 Department of Internal Medicine - HaematologyDepartment of Nuclear MedicineCharles University in Prague, Faculty of Medicine and University Hospital Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic.
authors: Ioannis
authors: I
authors: Svilias
authors: 4 Department of Internal Medicine - HaematologyDepartment of Nuclear MedicineCharles University in Prague, Faculty of Medicine and University Hospital Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic.
authors: Lukas
authors: L
authors: Smolej
authors: 4 Department of Internal Medicine - HaematologyDepartment of Nuclear MedicineCharles University in Prague, Faculty of Medicine and University Hospital Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic.
authors: Jitka
authors: J
authors: Cepkova
authors: 4 Department of Internal Medicine - HaematologyDepartment of Nuclear MedicineCharles University in Prague, Faculty of Medicine and University Hospital Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic.
authors: Jaroslav
authors: J
authors: Vizda
authors: 4 Department of Internal Medicine - HaematologyDepartment of Nuclear MedicineCharles University in Prague, Faculty of Medicine and University Hospital Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic.
authors: Petr
authors: P
authors: Sadilek
authors: 4 Department of Internal Medicine - HaematologyDepartment of Nuclear MedicineCharles University in Prague, Faculty of Medicine and University Hospital Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic.
authors: Ilona
authors: I
authors: Fatorova
authors: 4 Department of Internal Medicine - HaematologyDepartment of Nuclear MedicineCharles University in Prague, Faculty of Medicine and University Hospital Hradec Kralove, Sokolska 581, 50005 Hradec Kralove, Czech Republic.
authors: Pavel
authors: P
authors: Zak
mesh_terms: D000328:Adult; D001779:Blood Coagulation Factors / Q000378:metabolism; D005260:Female; D005342:Fibrinolysis / Q000187:drug effects; D020249:Hormone Replacement Therapy; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood* / Q000150:complications* / Q000209:etiology; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D010979:Platelet Function Tests; D011183:Postoperative Complications / Q000097:blood; D013927:Thrombosis / Q000209:etiology*; D013963:Thyroid Hormones / Q000097:blood*; D013964:Thyroid Neoplasms / Q000378:metabolism / Q000532:radiotherapy / Q000601:surgery; D013965:Thyroidectomy; D013974:Thyroxine / Q000627:therapeutic use
chemical_list: D001779:Blood Coagulation Factors; D007457:Iodine Radioisotopes; D013963:Thyroid Hormones; D013974:Thyroxine