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Triiodothyronine free (FT3)

SI UNITS (recommended)


* The SI units is the recommended method of reporting clinical laboratory results

Free T3, free triiodothyronine
Units of measurement
pmol/L, pg/mL, pg/dL, pg/100mL, pg%, ng/dL, ng/L

The thyroid hormones triiodothyronine (T3) and thyroxine (T4) are secreted into the bloodstream by the thyroid gland and play a vital role in regulating the body's metabolic rate, influencing the cardiovascular system, growth and bone metabolism, and are important for normal development of gonadal functions and nervous system.

T3 circulates in the bloodstream as an equilibrium mixture of free and serum bound hormone. Free T3 (fT3) is the unbound and biologically active form, which represents only 0.2‑0.4 % of the total T3. The remaining T3 is inactive and bound to serum proteins, while the distribution of T3 between these binding proteins (thyroxine binding globulin, pre - albumin, albumin) is controversially discussed.

The determination of free T3 has the advantage of being independent of changes in the concentrations and binding properties of the binding proteins; additional determination of a binding parameter (T‑uptake, TBG) is therefore unnecessary. Therefore free T3 is a useful tool in clinical routine diagnostics for the assessment of the thyroid status. Free T3 measurements support the differential diagnosis of thyroid disorders, are needed to distinguish different forms of hyperthyroidism, and to identify patients with T3 thyrotoxicosis.

SI units Conversion Calculator. Convert Triiodothyronine free (FT3) level to pmol/L, pg/mL, pg/dL, pg/100mL, pg%, ng/dL, ng/L . Clinical laboratory units online conversion from conventional or traditional units to Si units. Table of conversion factors for Triiodothyronine free (FT3) unit conversion to pmol/L, pg/mL, pg/dL, pg/100mL, pg%, ng/dL, ng/L .