Total triiodothyronine

10% to 20% of T3 is synthesized and released by the thyroid gland, and 80% to 90% of T4 is deiodized from surrounding tissues and converted to T3. T3 is a thyroid hormone that mainly exerts biological activity. The vast majority (99.5%) of T3 in serum bound to specific proteins in plasma, and only a few were free (0.5%). Changes in serum TT3 concentration indicate abnormal thyroid function. Changes in TT3 concentration are often parallel to TT4, but sometimes there are differences, such as T4 hyperthyroidism, and TT3 is normal. Therefore, TT3 and TT4 values ​​are often measured simultaneously in the clinic. Determination method: 2ml of venous blood, no anticoagulation, serum was separated for determination.