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Free T Calculation

Meaning

Free T Calculation is the determination of the biologically active, unbound fraction of thyroxine (T4) or triiodothyronine (T3) circulating in the blood, typically derived using complex algorithms or direct analog assays. This calculation is paramount in thyroid assessment because only the free hormone can readily enter target cells to exert its metabolic effects, irrespective of total hormone levels. Accurate calculation bypasses the confounding variables introduced by binding proteins like Thyroxine-Binding Globulin (TBG). This metric offers a clearer picture of true thyroid hormone availability at the tissue level.