INCREASED RISK OF AUTOIMMUNE THYROID-DISEASE IN HEPATITIS-C VS HEPATITIS-B BEFORE, DURING, AND AFTER DISCONTINUING INTERFERON THERAPY

Background: Thyroid gland dysfunction has been reported to occur with variable frequency during interferon alfa (IFN-alpha) therapy in patie nts with the hepatitis C virus (HCV). We prospectively evaluated if th e prevalence of autoimmune thyroid disease in patients with HCV differ s from that in patients with the hepatitis B virus (HBV) before, at th e end of, and 6 months after stopping treatment with IFN-alpha. Method s: One hundred thirty-four patients with HCV and 41 patients with HBV were studied. Measurements of serum free thyroxine, free triiodothyron ine, thyrotropin, thyroid peroxidase antibodies (TPOAbs), thyroglobuli n antibodies (TgAbs), and thyrotropin-binding inhibitory immunoglobuli n were performed. Results: Positive levels of TPOAb and TgAb were foun d in 20% and 11% of patients with HCV compared with 5% and 3% of patie nts with HBV, respectively. At the end of IFN-alpha therapy, thyroid g land dysfunction was more prevalent in patients with HCV (12%) compare d with those with HBV (3%), with thyrotropin levels significantly high er in the HCV group (P = .03). Titers of TPOAb, TgAb, and thyrotropin- binding inhibitory immunoglobulin increased significantly (P = .02, P = .04, and P = .02, respectively) at the end of IFN-alpha therapy in p atients with HCV but not in those with HBV. Patients who developed thy roid gland dysfunction were predominantly female (P = .03), had decrea sed levels of free triiodothyronine (P < .001), and had a higher preva lence of TPOAb (P = .03) before treatment with IFN-alpha. Thyroid glan d dysfunction was reversed in 60% of those with HCV 6 months after dis continuing treatment with IFN-alpha. Conclusions: Patients with HCV ar e more susceptible than patients with HBV to autoimmune thyroid diseas e. Systematic screening of thyroid gland function and TPOAb titers in all patients with HCV before, during, and after IFN-alpha therapy appe ars warranted. This precaution is not necessary for patients with HBV.