Interferon-α-induced hyperthyroidism: a three-stage evolution from silent thyroiditis towards Graves’ disease

Abstract

Autoimmune thyroid disease is a common side-effect of interferon-α (IFN-α) treatment of viral hepatitis C. We have described three patients with hepatitis C for whom IFN-α and ribavirin were prescribed and who developed two successive phases of silent thyroiditis followed by hyperthryroidism relapse due to Graves’ disease. These three men had no known history of familial or personal thyroid disease. Destructive thyrotoxicosis appeared 4–6 months after starting IFN-α, followed by Graves’ hyperthyroidism within 8 to11 months. The thyrotropin (TSH) level was normal before IFN-α was started. The diagnosis of destructive thyroiditis was confirmed by anti-TSH receptor antibody (TSHRAb) negativity and the absence of radionuclide (123I or 99Tc) uptake on thyroid scintiscans. Eight to eleven months after starting treatment, TSHRAb positivity and intense scintigraphic uptake confirmed the appearance of Graves’ disease. IFN-α was continued in only one patient. Hence, hyperthyroidism induced by IFN-α could correspond to the first phase of silent thyroiditis, to Graves’ disease or to the succession of both. Rigorous diagnostic procedures with repeated scintiscans and TSHRAb titering are necessary to avoid a false diagnosis and inappropriate therapy.