title: Effects of levothyroxine treatment on biochemical and hemostasis parameters in patients with hypothyroidism.
abstract: OBJECTIVE
  The aims of the study were to evaluate the disturbances in the coagulation system in patients with overt hypothyroidism (OH), to assess the effects of levothyroxine (LT4) on the coagulation parameters, and to determine whether subclinical hypothyroidism (SH) affects concentrations of coagulation markers and several biochemical parameters, thereby supporting early substitution.
  
  
  METHODS
  The study included 15 patients with SH (TSH levels 5-10 mU/l), 15 patients with OH and 15 euthyroid controls.
  
  
  METHODS
  Blood urea nitrogen, creatinine, creatine phosphokinase, aspartate aminotransferase, lactate dehydrogenase, total-cholesterol, high density lipoprotein-cholesterol, low density lipoprotein-cholesterol and triglyceride levels, and bleeding time, prothrombin time (PT), activated partial thromboplastin time (APTT), factor VIII activity, von Willebrand factor activity (vWF), platelet count and clotting time were evaluated just before and three months after the maintenance of euthyroidism with LT4 treatment.
  
  
  RESULTS
  Factor VIII and vWF activities were lower in patients with SH than in controls (P < 0.01). Increased bleeding time, PT, APTT and clotting time and decreased factor VIII activity and vWF activity were observed in patients with OH when compared with controls. Bleeding time, PT, APTT and clotting time decreased and factor VIII activity, vWF and platelet count increased after LT4 in patients with OH. Increases in factor VIII activity and vWF (P < 0.01) were detected also in the SH group with treatment.
  
  
  CONCLUSIONS
  OH is associated with significant abnormalities in clotting parameters which are reversed by LT4. In contrast, SH is associated with minor changes in factor VIII activity and vWF which are reversible by LT4. Serum lipids and other measured parameters are not improved by LT4 in patients with TSH < 10 mU/l and these data fail to demonstrate a need to treat such patients.
authors.affiliation: Ankara University, School of Medicine, Department of Endocrinology and Metabolic Diseases, Ibn-i Sina Hospital, Sihhiye 06 100, Ankara, Turkey. sevim.gullu@temd.org.tr
authors.forename: Sevim
authors.initials: S
authors.lastname: Gullu
authors.forename: Hasan
authors.initials: H
authors.lastname: Sav
authors.forename: Nuri
authors.initials: N
authors.lastname: Kamel
mesh_terms: D000328:Adult; D000368:Aged; D005169:Factor VIII / Q000378:metabolism; D005260:Female; D006487:Hemostasis / Q000187:drug effects*; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy* / Q000378:metabolism* / Q000503:physiopathology; D008875:Middle Aged; D012720:Severity of Illness Index; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000503:physiopathology; D013974:Thyroxine / Q000627:therapeutic use*; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D014841:von Willebrand Factor; D005169:Factor VIII; D013974:Thyroxine