Interferon (IFN) alpha treatment for various conditions has been associated with thyroid autoimmunity. The incidence of interferon induced thyroid autoimmunity has been reported to range from 2.5% to 42%, possibly depending upon dose and duration of medical therapy and patient characteristics. It is not known whether IFN-alpha initiates autoimmune thyroid disease (AITD) or simply exacerbates AITD in individuals with subclinical AITD.