The FT3, FT4, and TSH blood tests are used to assess thyroid gland function with a focus on the active (free) thyroid hormones:
FT3 (Free Triiodothyronine) – Measures the unbound, active form of T3 in the blood. Helps detect hyperthyroidism.
FT4 (Free Thyroxine) – Measures the unbound, active form of T4. Useful for evaluating both hypothyroidism and hyperthyroidism.
TSH (Thyroid Stimulating Hormone) – Produced by the pituitary gland, TSH controls the production of T3 and T4. It is a primary marker for thyroid function.
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