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Free T Bioavailability Metrics

Meaning

Free T Bioavailability Metrics represent the critical laboratory indices that quantify the fraction of circulating thyroxine ($text{T}_4$) and triiodothyronine ($text{T}_3$) hormones that are unbound by plasma proteins. This unbound fraction is the only component capable of diffusing into tissues to exert genomic and non-genomic effects on cellular metabolism and differentiation. Accurate assessment of these metrics is paramount because total hormone levels can be misleading due to variations in thyroid-binding globulin (TBG) capacity. We prioritize these values to truly gauge the functional thyroid status of the patient.