[Side effects during interferon-alpha therapy of hepatitis C with special consideration of thyroid dysfunction]

Hepatitis C virus infection is a worldwide problem and its natural, unfavorable course is still a challenge for the hepatologist. The standard of treatment is combined therapy with interferon-alpha and ribavirin. This therapy is related to a wide spectrum of side effects that significantly reduce quality of life. Approximately 90% of patients suffer from at least one adverse effect; 15% will therefore have reduced drug dose and 5% will discontinue treatment. The most common acute side effects are flu-like symptoms and chronic effects are hematological, neuropsychiatric, and endocrinological (mainly the thyroid). The latest classification divides interferon-induced thyroid diseases into two groups: autoimmune (Hashimoto disease, Graves-Basedow disease, positive antithyroid autoantibodies in euthyroid patients) and non-autoimmune (destructive thyroiditis, non-autoimmune hypothyroidism). The most common complication of cytokine therapy is the induction of antithyroid autoantibodies de novo without thyroid dysfunction. It seems that destructive thyroiditis with typical biphasic course is more common in therapeutic regimens with ribavirin than in interferon-alpha monotherapy. Clinically overt pathologies very often have very discrete symptoms which cause diagnostic and therapeutic dilemmas. Interferon-induced thyroid disorders are usually mild and sometimes self-limiting; nevertheless, every overt thyroid disease requires endocrinological consultation and possible treatment. In this review the most important current information related to hepatitis C, interferon alpha and ribavirin therapy, and thyroid disorders is collected. A new classification of interferon-induced thyroid disease is proposed.