TPO and thyrotoxicosis: Although asymptomatic, follow-up testing revealed biochemical thyrotoxicosis (peak FT4 of 3.9 ng/dL and TSH of 0.01 mIU/mL), with anti-TPO and anti-TG Ab levels at 308 IU/mL and 147 IU/mL, respectively, and negative TBII and TSIG antibody levels.