Phenotypic Expression and Challenges of a Distinct Form of Thyrotoxicosis

Triiodothyronine (T3)-predominant Graves disease is characterized by persistently high serum T3 level and normal or low serum thyroxine (T4) level during thionamide drug therapy. Graves disease is much more aggressive in this form and has a lower remission rate with antithyroid drugs (ADI) and radioiodine (I-131) therapy. An 18-year-old Chinese woman had thyrotoxicosis with overt features of T3-predominant Graves disease. She failed to achieve a remission despite ADI treatment for 4 years and 3 doses of I-131 therapy. She finally underwent a total thyroidectomy followed by I-131 remnant ablation. The pathogenetic mechanisms, and the reasons for a tendency for nonremission with ADI, and I-131 therapy are discussed.