The most common tests are T3, T4, FT3, TF4 and TSH. T3 and T4 are thyroid hormones secreted by the thyroid gland, which bind to proteins in the blood serum but must be separated from the proteins in the blood when they are to function, so measuring free thyroid hormones FT3 and FT4 better reflects the function of the thyroid gland. TSH is a thyroid stimulating hormone secreted by the pituitary gland, which is like a dispatcher sent by the brain to regulate the work of the thyroid gland. If there is less thyroid hormone in the body, that is, when the thyroid gland is hypothyroid, TSH will rise and promote the thyroid gland to produce more thyroid hormone; on the contrary, in hyperthyroid patients, because there is already too much thyroid hormone in the body, TSH will be reduced to a very low level. Some antibody indicators such as TPO-Ab, TG-Ab, and TR-Ab. Patients with chronic inflammation of the thyroid gland need to have TPO-Ab and TG-Ab checked because they reflect the patient’s inflammatory status, and sometimes after a period of treatment, these two indicators may drop, but usually not to normal. For patients suspected of hyperthyroidism, TR-Ab should also be checked. An abnormally high level may indicate primary hyperthyroidism. In addition to the above 8 indicators, doctors sometimes prescribe calcitonin (CT), thyroglobulin (TG), parathyroid hormone (PTH) and other indicators for different patients, the significance of the specific indicators should be analyzed in the context of the condition.