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endocrinology

Free Thyroxine

Free T4· also: Free T4, fT4

Clinical Overview

Free T4 is the active, unbound form of thyroxine. Low Free T4 with high TSH confirms hypothyroidism; high Free T4 with low TSH confirms hyperthyroidism.

Reference RangesWHO/IFCC standards

Age GroupReference RangeUnitNotes
Adults (18–64)0.8 – 1.8ng/dL

Also reported in: pmol/L.Conversion factor: 1 pmol/L = 12.870 ng/dL.

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Related Topics

thyroidT4TFThypothyroidism

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