Prevalence and significance of thyroid autoantibodies in patients with chronic hepatitis C virus infection: A prospective controlled study

OBJECTIVE: To clarify controversies on the prevalence and clinical significance of thyroid autoimmunity in hepatitis C virus (HCV) infection. DESIGN: A prospective controlled and follow-up study. PATIENTS AND MEASUREMENTS: Serum thyroid microsomal antibody (TMA) and thyroid stimulating hormone were assayed and compared in a consecutive, unselected series of 130 patients with chronic HCV infection, 130 sex/age (± 2 years)-matched patients with chronic hepatitis B virus (HBV) infection and 260 matched normal controls. RESULTS: The prevalence of thyroid autoantibodies in male patients with chronic HCV was <2%. The prevalence of TMA (<1:400) in female patients with chronic HCV infection was significantly higher than that of HBV controls (22.1 vs. 1.6%; P < 0.001), and higher but not significant compared with normal controls (13.5%). However, the trend of increasing prevalence with age in normal controls was not observed in HCV patients. TMA seropositive female HCV patients were not different from seronegative counterparts in age, duration of infection, HLA haplotype, associated autoantibodies and liver histology but had a significantly higher prevalence of genotype 1b/2b mixed infection (P < 0.01) and anti-GOR (P < 0.05). Of the 23 HCV patients seropositive for thyroid autoantibodies, seven had Hashimoto's thyroiditis, two had Graves' disease and three had received subtotal thyroidectomy. During follow-up, four of 15 female patients showed a 14-16-fold increase in TMA titre and one developed hyperthyroidism. Patients with thyroid autoantibodies did not show a propensity to develop thyroid dysfunction during interferon therapy. CONCLUSIONS: These results suggest a weak association between HCV and thyroid autoimmunity in females. As in the ordinary population with thyroid autoantibodies, they should be evaluated for thyroid status and be followed-up if thyroid autoimmunity is evident. However, seropositivity of thyroid autoantibodies is not a contraindication to interferon therapy.