Free T4 (Free Thyroxine)
Free T4 is the active fraction of the thyroid hormone thyroxine. Together with TSH, it shows how well the thyroid gland works.
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Normal ranges
Adults: 9–22 pmol/L.
Units: pmol/L
Causes of deviations
Low levels:
Hypothyroidism, iodine deficiency, thyroiditis.
High levels:
Hyperthyroidism, thyroid hormone overdose, thyroiditis (early phase).
When to see a doctor
If abnormal together with TSH — for thyroid evaluation.
Related biomarkers
Panels
Thyroid panel
Conditions
HypothyroidismHyperthyroidism
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