Graves' hyperthyroidism showing transient hypothyroidism during interferon therapy for chronic hepatitis type C.

We report a patient with Graves' disease in whom thyroid function was changed from initial hyperthyroidism to transient hypothyroidism and back to hyperthyroidism during interferon (IFN) therapy. A 43-year-old man was admitted to our hospital to receive IFN treatment for chronic active hepatitis (type C) in June 1998. His thyroid function was normal and testing for thyroid gland antibodies (TSH binding inhibitor immunoglobulins; TBII, anti-thyroglobulin antibodies; TgAb and anti-thyroid peroxidase antibodies; TPOAb) was negative before IFN therapy. The patient had neither history of thyroid disease nor any particular family history. He developed hyperthyroidism four months after its initiation of IFN therapy. When he was hyperthyroid, TBII, the activity of thyroid-stimulating antibodies (TSAb) and thyroid stimulation-blocking antibodies (TSBAb) were 40.2% (normal range, -15 approximately +15.0%), 1201% (normal range,