Résumé
The interferon are naturally induced proteins by the immune system. They have biologic and clinical demonstrations of auto-immunity. Among these demonstrations thyroid anti-body apparition and emergence of dysthyroidism notably the Graves disease. We present a case of a woman followed up for a chronic hepatitis C. Her treatment was interferon and ribavirine and she developed hyperthyroidism. The stop of the antiviral treatment and the administration of anti thyroid were sufficient to treat this affection. It can be encouraged by factors notably age, sex and presence of TPO antibody. The C virus can induce dysthyroidism. The clinical and biological symptoms were similar to the spontaneous Graves disease. The follow up of interferon therapy for chronic hepatitis C was very important