Change in von Willebrand factor and carotid intima-media thickness in hypothyroid patients with normal thyroid function after levothyroxine replacement therapy.

OBJECTIVE: This study examined whether levothyroxine (L-T4) replacement might affect serum markers of endothelium injury, including von Willebrand factor (vWF), factor VIII activity and thrombomodulin (TM), during normalization of increased intima-media thickness (IMT) in the common carotid artery (CCA) in hypothyroid patients after L-T4 replacement therapy.

PATIENTS AND METHODS: Thirty-three hypothyroid patients were examined for vWF, factor VIII, TM and CCA IMT before and after 1 year of normalization of thyroid function by L-T4 replacement. CCA IMT was measured from digitized still images taken during scanning by high-resolution ultrasonography as an indicator of early atherosclerosis.

RESULTS: Serum factor VIII and vWF increased significantly during 1 year of normalization of thyroid function (from 122.7+/-9.4 to 151.3+/-18.8% (P<0.05) and from 109.9+/-9.6 to 135.2+/-12.4% (P<0.005) respectively), although these values all fell within the respective normal range. Serum TM, in contrast, did not change appreciably in response to L-T4 treatment, moving from 2.57+/-0.15 to 2.74+/-0.18 ng/ml (P=0.086). During 1 year of a euthyroid state, all patients showed a significant decrease in CCA IMT (P<0.0001). Change in serum vWF, but not in factor VIII or TM, showed a positive correlation with that of CCA IMT during L-T4 replacement therapy. Furthermore, the change in serum vWF was significantly and independently associated with change in CCA IMT (r=0.490, P=0.0038).

CONCLUSIONS: The present study demonstrated that the improvement of CCA IMT during L-T4 treatment might have the potential to attenuate an elevation of vWF and to attenuate vascular injury by the cardiovascular effects of thyroid hormone in hypothyroid patients.