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T3 T4 Free

Meaning

T3 T4 Free refers to the unbound, biologically active concentrations of the two primary thyroid hormones circulating in the bloodstream: triiodothyronine (T3) and thyroxine (T4). Since over 99% of these hormones are bound to carrier proteins like Thyroxine-Binding Globulin (TBG), only the small, free fraction is able to enter cells and bind to nuclear receptors to exert metabolic effects. Clinically, the measurement of Free T3 and Free T4 provides the most accurate assessment of the body’s true thyroid status and metabolic drive. This is the crucial indicator for diagnosing and managing thyroid dysfunction.