Two weeks later, repeat testing showed an undetectable TSH, free thyroxine (free T4) 2.7 ng/dL (normal range: 0.70-1.48 ng/dL), total triiodothyronine (T3) 5.08 ng/mL (normal range: 0.40-1.93 ng/mL), thyrotropin receptor antibody (TRAb) 20.3 IU/L (reference range: ≤1.75 IU/L), thyroid stimulating immunoglobulin (TSI) 2.3 IU/L (reference range: ≤0.54 IU/L), thyroid peroxidase antibody (TPO) 7.66 IU/mL (reference range: <5.61 IU/mL), confirming hyperthyroidism due to Graves' disease. The gene discussed is TPO; the disease is hyperthyroidism.