Free Thyroxin index (FTI)
Frequently Asked Questions
T7, or the Free Thyroxine Index, is a numerical figure that may be used as a rough estimate of free thyroxine (FT4) concentrations in the blood. Free thyroxine hormone (FT4) is the physiologically active type of thyroid hormone, and its concentration is measured here.
Hypothyroidism, in which the thyroid gland is underactive, can be indicated by a low Free Thyroxine Index (FTI). A low FTI value suggests low free T4 levels, as the FTI is dependent on these levels.
If your Free Thyroxine Index is high, it probably means your blood has too much free thyroxine (FT4). The thyroid gland’s major hormone, thyroxine, is essential for maintaining proper metabolic and other physiological functions. An elevated FT4 level is indicative of hyperthyroidism, a disease characterized by elevated levels of thyroid hormone.
As a quantitative measure of thyroid health, the Free Thyroxine Index (FTI), also known as the Thyroxine Index (TI), is a useful metric. It is calculated by determining the serum protein concentrations that bind thyroxine (T4). Since direct measurement of free thyroxine (FT4) is now deemed more precise, the FTI is no longer routinely used in clinical practice.
Multiplying the total thyroxine (T4) concentration by the thyroxine-binding globulin (TBG) resin uptake (RU) yields the FTI. The FTI is a surrogate for free thyroxine since it accounts for the presence of thyroxine-binding proteins (TBG) in the blood. Thyroxine is inactive while bound to these proteins and is only accessible to the body’s tissues in its free, active state.