The tests include: Thyroid binding globulin (TBG): This is the specific protein that binds to T4 and T3. T3 resin uptake (T3RU): This calculates the percentage of TBG in the blood. Thyroid blood ...

in the presence of medications that displace T4 from TBG; during critical phases of NTI; and in pregnancy (see Table 1). The frequency of these FT4 assay artifacts suggests that TSH or the TSH/FT4 ...

[154] "Classic" uptake assays used T3 tracer because the lower T3-TBG binding affinity relative to T4-TBG resulted in a higher isotopic uptake by adsorbant and thus shorter counting times.