Triiodothyronine (T3) is the hormone principally responsible for the development of the effects of the thyroid hormones on the various target organs.
T3 (3,5,3'‑triiodothyronine) is mainly formed extrathyroidally, particularly in the liver, by enzymatic 5'‑deiodination of T4. Accordingly, the T3 concentration in serum is more a reflection of the functional state of the peripheral tissue than the secretory performance of the thyroid gland. A reduction in the conversion of T4 to T3 results in a decrease in the T3 concentration. It occurs under the influence of medicaments such as propranolol, glucocorticoids or amiodarone and in severe non - thyroidal illness (NTI), and is referred to as “low T3 syndrome”. As with T4, over 99 % of T3 is bound to transport proteins. However, the affinity of T3 to them is around 10‑fold lower.
The determination of T3 is utilized in the diagnosis of T3‑hyperthyroidism, the detection of early stages of hyperthyroidism and for indicating a diagnosis of thyrotoxicosis factitia.
SI units Conversion Calculator. Convert Triiodothyronine (T3) level to nmol/L, ng/mL, ng/dL, ng/100mL, ng%, ng/L, µg/L. Clinical laboratory units online conversion from conventional or traditional units to Si units. Table of conversion factors for Triiodothyronine (T3) unit conversion to nmol/L, ng/mL, ng/dL, ng/100mL, ng%, ng/L, µg/L.