It is usually better to take the test in the morning on an empty stomach. Thyroid Function Test includes thyroid stimulating hormone (TSH), total thyroxine (TT4), free thyroxine (FT4), total triiodothyronine (TT3) and free triiodothyronine (FT3). The Five Thyroid Functions are indicators reflecting the physiological and functional status of the thyroid gland, of which TSH is a thyroid-stimulating hormone secreted by the pituitary gland, which promotes the growth of the thyroid gland and the secretion of thyroid hormones, and is the most sensitive indicator for diagnosing primary hypothyroidism. TT4, TT3, FT3, FT4 are hormones secreted by the thyroid gland itself, and are indicators of thyroid function, of which FT4 and FT3 have better sensitivity and specificity. The reference ranges of thyroid function in different laboratories are different due to different laboratory testing methods, usually the reference ranges of each index are as follows: FT4 11.5-22.7 pmol/L, FT3 3.5-6.5 pmol/L, T3 0.6-1.81 ng/ml, T4 45-109 ng/ml, TSH 0.35-5.5 μIU/ml. If abnormal thyroid function is found, it is recommended to go to the hospital.