Plasma levels of free tissue factor pathway inhibitor in patients with various thyroid disorders

Various coagulation abnormalities occur in thyroid disorders and its range may vary from subclinical laboratory abnormalities to clinically significant disorders of coagulation. Tissue factor pathway inhibitor (TFPI), which inhibits the initial reaction of tissue factor mediated coagulation pathway, is reported to be increased in patients with Graves disease (GD) in one study. Hyperthyroid (n=10), hypothyroid (n=10) and subclinical hypothyroid (n=10) patients and control cases (n=16) were evaluated for free and total tissue factor pathway inhibitor (tTFPI), plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (tPA) levels in disease and euthyroid states. Free TFPI levels were significantly higher in hyperthyroid patients compared with the control group and subclinic hypothyroid patients (p<0.001), but not with hypothyroid patients (p>0.05). After the euthyroid state was obtained in the hyperthyroid group, the levels of total TFPI (p<0.05), free TFPI (fTFPI) (p<0.005), t-PA (p<0.005) and PAI-1 (p<0.02) decreased significantly. In hyperthyroid patients, there was a strong correlation between thyroid functions and free TFPI levels. In conclusion, we hypothesize that coagulation abnormalities seen in thyroid disorders cannot be explained directly with the impaired fibrinolytic activity but also with the elevated fTFPI levels. Both increased plasma fTFPI and PAI-1 levels could be markers of the peripheral activity of thyroid hormones.