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Total triiodothyronine in blood
Medical expert of the article
Last reviewed: 29.07.2022
The reference values (norm) of concentration T 3 (triiodothyronine) in blood serum are 1.08-3.14 nmol / l.
T 3 (triiodothyronine) is formed and synthesized by the thyroid gland, but the bulk of T 3 is formed outside the thyroid gland during deiodination of T 4. Approximately 99.5% of T 3 circulating in the blood is bound to proteins. The elimination half-life of the blood is 24-36 hours. The activity of T 3 is 3-5 times that of T 4.
Determination triiodothyronine very informative when T 3 -tireotoksikoze, since in many cases the concentration of T 4 does not change significantly (sharply elevated concentration only T 3 ).
With myeloma, producing a large amount of IgG, as well as with severe liver diseases, false-positive values of triiodothyronine concentration are recorded.
In elderly people, and in patients with severe medical conditions often observed so-called syndrome low T 3 - decrease in its concentration in the serum with normal T 4. The syndrome of low triiodothyronine in this contingent of individuals is not a sign of hypothyroidism.