We report the case of thyroid dysfunction that developed in a 36-year-old female patient who required combination therapy with interferon and ribavirine for chronic hepatitis C. Firstly. she suffered a hyperthyroidism followed by a hypothyroidism stage requiring thyroxine replacement therapy, Nevertheless, combination treatment was not discontinued, reaching a sustained biochemical and virological response. The pathogenesis of autoimmune diseases in patients with Hepatitis C virus infection and interferon therapy is not clear. but usually these disorders are reversible and only require supervision and treatment if clinical or laboratory abnormalities are present.