Biomarker Reference · FT3
Free Triiodothyronine (FT3) is a clinical biomarker used in thyroid-endocrine assessment. Free triiodothyronine is the active thyroid hormone, generated predominantly by peripheral deiodination of T4 in liver, kidney, and other tissues via type 1 and type 2 deiodinases. It is measured in 5 laboratory tests on BiomarkersLabs.com.
Free triiodothyronine is the active thyroid hormone, generated predominantly by peripheral deiodination of T4 in liver, kidney, and other tissues via type 1 and type 2 deiodinases. It binds nuclear thyroid receptors to regulate metabolism, and its free fraction reflects tissue-available hormone. Dried blood spot fT3 correlates with serum fT3 when platform-validated.
Free T3 provides insight into peripheral thyroid hormone activation and tissue thyroid status, particularly in patients on levothyroxine monotherapy who convert T4 to T3 variably. It is the key diagnostic marker in T3 thyrotoxicosis and is used to assess adequacy of combination T4/T3 therapy. Dried blood spot FT3 offers a practical alternative when repeated venepuncture is burdensome.
Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.
5 tests on BiomarkersLabs.com include this biomarker.
Free Triiodothyronine reference range in this test: Approximately 2.3–4.2 pg/mL; assay- and method-specific.
Free Triiodothyronine reference range in this test: Approximately 2.3–4.2 pg/mL (3.5–6.5 pmol/L); method-dependent.
Free Triiodothyronine reference range in this test: Approximately 2.3–4.2 pg/mL; method-specific intervals apply.
Free Triiodothyronine reference range in this test: Platform-dependent; typical serum ranges ~2.3–4.2 pg/mL.
Free Triiodothyronine reference range in this test: Method-specific for dried blood spot; approximate serum equivalents 3.5–6.5 pmol/L.
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