Interferon-associated thyroid dysfunction in anti-D-related chronic hepatitis C

To assess the frequency and nature of thyroid abnormality in association with interferon (IFN) therapy alone and in combination with ribavirin, 19 patients receiving IFN therapy for hepatitis C virus (HCV)-induced liver disease had thyroid function tests assessed on a monthly basis. Group I (n = 9) patients received 5 million U of IFN s.c. daily for 2 weeks, followed by 3 million U three times per week for 6 months. Group II (n = 10) patients received 3 million U IFN s.c. three times per week together with ribavirin 400 mg twice daily orally for 6 months. Five of 19 patients (26.3%) developed thyroid abnormalities, 3 (33.3%) in group I and 2 (20%) in group II. Three patients developed thyroid function tests consistent with hyperactivity, and 2 of these normalized on cessation of IFN therapy. One patient continued on IFN but remained clinically euthyroid with antithyroid treatment. Two patients developed thyroiditis and required thyroid supplementation. (One of the 2 had pretreatment antimicrosomal thyroid antibodies and a positive family history of thyroid disease.) Of the 3 patients with HCV type 1b, 1 had pretreatment thyroid antibodies, and all 3 had antibodies during IFN therapy. Neither of the 2 patients with genotype 3 had pre-IFN or post-IFN thyroid antibodies. Patients on IFN therapy need regular thyroid function testing. The frequency of abnormal thyroid tests may be dose related. HCV genotype may influence the development of thyroid antibodies.