The five thyroid function tests include total T3, total T4, free T3, free T4, and thyroid stimulating hormone TSH. T4 is thyrotropine containing tetraiodine. Total T4 is the sum of bound thyroxine and free free thyroxine. The reference values for free T4 are 9 to 25 pmol/L and for total T4 are 64 to 154 nmol/L. T3 is the triiodine-containing thyrotropine formed after deiodination of T4 in the liver and in the kidney. Total T3 is the sum of bound thyroxine and free free thyroxine. The reference values for free T3 are 2.1 to 5.4 pmol/L and for total T3 are 2 to 2.9 nmol/L. Thyroid stimulating hormone TSH is a hormone responsible for regulating the secretion of the thyroid gland, which promotes the proliferation of thyroid cells and increases the synthesis and secretion of thyroid hormones. Changes in the indicators of thyroid function tests generally reflect the functional status of the thyroid gland and related pathologies, and different fluctuations in the indicators often indicate different diseases. Abnormalities in thyroid function tests must be scientifically diagnosed under the guidance of a professional doctor.