Triiodothyronine resin uptake test

When the plasma TBG level and binding force are normal, the extent of its binding to T4 is affected by the plasma T4 level. The higher the T4 concentration, the higher the saturation of TBG, and vice versa. Therefore, measuring the amount of TBG that is not bound to T4 in blood can indirectly reflect the plasma T4 concentration. In the test, a quantitative exogenous 125I-T3 was added to the blood sample to be tested, and it was combined with TBG that was not bound to T4, and then the remaining 125I-T3 was adsorbed with an adsorbate (resin, red blood cells). Measuring the amount of 125I-T3 bound to TBG can indirectly understand the level of T4 in the blood. This test is not for measuring T3 in blood. In order to avoid misunderstanding, it is recommended to rename this test as "TBG binding test".