TPO and hypothyroidism: Thyroid function tests indicated severe hypothyroidism with an elevated thyroid-stimulating hormone (TSH) level of 845.6 μIU/mL (normal range 0.4-4.4), low levels of FT3 (0.3 pmol/L; normal range 9.8-16.3), and FT4 (0.388 pmol/L; normal range 9.8-16.3), along with highly positive anti-thyroid peroxidase antibodies (1,796.5 U/mL; normal value < 34) and an anti-thyroglobulin level of 359 μg/L (normal value < 25 μg/L).