Thyroglobulin is a test that reflects the function of the thyroid gland and contains five important data, namely FT3 (free triiodothyronine), FT4 (free thyroxine), TT3 (total triiodothyronine), TT4 (total thyroxine), and TSH (thyroid-stimulating hormone). There is no one item that is the most important of the five thyroid function tests, they are all important and each one has its own significance. 1. TSH is the most sensitive indicator of thyroid function and is important for the diagnosis of subclinical hyper- or hypothyroidism. 2. TT3 and TT4 are the most basic screening indicators for thyroid function, stable and reproducible, but affected by the amount of total serum protein, for example, pregnancy, estrogen, acute viral hepatitis may cause TT3 and TT4 to be high; androgens, glucocorticoids, and hypoproteinemia may cause TT3 and TT4 to be low. 3. FT3 and FT4 are not affected by total serum protein and can directly reflect the state of thyroid function, which is the main indicator for diagnosing clinical hyper- or hypothyroidism. Patients with abnormal thyroid function should go to the hospital and be treated under the guidance of a doctor.