In patients with Graves' disease treated with inorganic iodine, serum rT3 concentrations increase,31,32 serum T3 concentrations rapidly decrease, and the serum T4/T3 ratio is significantly increased.33 These data suggest that DIO1 is involved in iodine autoregulation and DIO3 is sensitive to inorganic iodine. This evidence concerns the gene DIO1 and Graves disease.