Biochemical thyrotoxicosis without clinical symptoms developed after 4 months (peak FT4 of 2.4 ng/dL and TSH of 0.01 mIU/mL) with repeat anti-TPO and TG antibody levels at >1000 IU/mL and 147 IU/mL, respectively, and TBII and TSIG remaining negative. This evidence concerns the gene TPO and thyrotoxicosis.