Incidence of autoimmune thyroiditis in interferon-alpha treated and untreated patients with chronic hepatitis C virus infection.

OBJECTIVES: To clarify the relationship between interferon-alpha (IFN-alpha) therapy and autoimmune thyroiditis in chronic hepatitis C virus (HCV) infection, we investigated a selected number of patients without basal thyroid dysfunctions.

MATERIALS AND METHODS: 130 patients (average age: 20-70), with chronic HCV infection and without basal clinical and laboratory signs of autoimmune thyroiditis were divided into two groups: IFN-alpha treated (A) and untreated (B) patients. Group A received IFN-alpha (three million U.I./3 times a week) for six months; group B was followed for the same period. Thyroid peroxidase and thyroglobulin autoantibodies were measured by radioimmunoassay; thyroid function was measured by radioimmunoassay (free thyroxine and triiodothyronine) and immunoradiometric assay (thyroid stimulating hormone).

RESULTS: After a 6-month period, thyroid autoantibodies positivity was documented in 21.1% of group A and in 10.3% of group B patients, both statistically relevant (p<0.001 and p<0.011, respectively). The comparison between the two groups was not statistically relevant (p=0.142).

CONCLUSIONS: Our study showed a prevalence of de novo thyroid autoimmunity in chronic HCV patients treated with IFN-alpha, confirming previous data in literature. The lack of a significant difference between treated and untreated patients strongly suggests that the anti-thyroid autoimmune response is linked to the HCV infection itself. Moreover, IFN-alpha therapy probably does not represent a risk factor in renewing the autoimmune processes of the thyroid gland. Thyroid function and autoantibodies must be systematically monitored in patients with HCV infection, especially in female and IFN-alpha treated population, not only to verify the possible thyroid abnormalities but also to rule out concomitant autoimmune diseases.