Effect of levothyroxine suppression therapy on plasma thrombin activatable fibrinolysis inhibitor antigen levels in benign thyroid nodules.

OBJECTIVE The aim of this prospective study was to investigate the effect of LT4 suppression therapy on plasma thrombin activatable fibrinolysis inhibitor (TAFI) antigen and plasminogen activator inhibitor-1 (PAI-1) levels in benign thyroid nodules. We also compared hyperthyroid patients and healthy controls. SUBJECTS AND METHODS Twenty premenopausal women with benign thyroid nodules were given LT4 suppression therapy for 1 year. Plasma TAFI and PAI-1 antigen levels were measured at baseline and after LT4 suppression treatment. The endogenous hyperthyroid group was composed of 19 premenopausal females with newly diagnosed endogenous hyperthyroidism. Eighteen age-matched euthyroid healthy premenopausal women were enrolled as the control group. RESULTS TAFI antigen levels decreased after LT4 suppression treatment; however, the difference was not statistically significant (p = 0.057). LT4 treatment resulted in a nonsignificant increase in PAI-1 levels. Patients with endogenous hyperthyroidism had decreased levels of TAFI antigen and increased levels of PAI-1 antigen (p < 0.05). There was a negative correlation between the FT(4) and TAFI antigen levels. Serum TSH was positively correlated with the plasma levels of TAFI antigen. CONCLUSION LT4 suppression therapy for benign thyroid nodules did not result in a significant decrease in TAFI antigen levels in premenopausal women, but endogenous hyperthyroidism was associated with significantly decreased levels of TAFI antigen.