Total triiodothyronine in blood
Last reviewed: 29.07.2022
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
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.