Thyroid function test is called thyroid function test, the main test items are thyroxine, thyroid stimulating hormone and other five items, used to determine the patient’s thyroid function. Thyroid function test is a common clinical test to determine whether the patient’s thyroid function is normal or not, and the main test items are thyroxine, free thyroxine, triiodothyronine, free triiodothyronine and thyrotropin. Doctors can determine whether a patient has a thyroid disorder such as hyperthyroidism by the increase or decrease in the levels of these five hormones. First, if a patient’s free thyroxine and free triiodothyronine levels are elevated, but thyrotropin levels are low, a preliminary diagnosis of hyperthyroidism is usually made. A preliminary diagnosis of hypothyroidism may be made if the patient has decreased levels of free thyroxine and free triiodothyronine but increased levels of thyrotropin. Thyroid function tests are clinically important, and it is recommended that patients with recent thyroid function abnormalities seek medical attention as soon as possible for active treatment under the guidance of a physician.