What Is Free Thyroxine?
Thyroxine is a hormone synthesized and secreted by thyroid follicular epithelial cells. Pregnancy, breastfeeding, liver cirrhosis, nephrotic syndrome, etc. can change the concentration of serum thyroxine-binding globulin and its binding power, and change the concentration of free thyroxine. The determination of free thyroxine is not affected by serum binding proteins (mainly TBG), and is a sensitive indicator of in vitro tests of thyroid function. Even when changes in serum thyroxine-binding globulin concentration and binding force are caused under physiological and pathological conditions, it can more accurately reflect the function of the thyroid gland.
Basic Information
- Chinese name
- Free thyroxine
- Foreign name
- FreeThyroxine.FT4
- Function
- Achieve the biological effects of this hormone
- Normal value
- 11.5 ~ 22.7
- Clinical significance
- FT4I is an indicator that indirectly reflects FT4
- Medical value
- The preferred indicator for the diagnosis of clinical hyperthyroidism
Clinical significance of free thyroxine
- Tetraiodothyronine (T 4 ) is part of the thyroid physiological regulation system. It has an effect on total metabolism. Most of T 4 binds to its transport proteins (TBG, prealbumin, albumin). FT 4 measurement is an important part of routine clinical diagnosis. When thyroid dysfunction is suspected, FT 4 and thyroid stimulating hormone (TSH) are often measured together. FT 4 is also suitable for monitoring thyroid suppression therapy. The advantage of the FT 4 assay is that it is not affected by changes in its binding protein concentration and binding characteristics. Serum FT 4 is a sensitive indicator of in vitro test of thyroid function. It can reflect the function of thyroid more accurately when the TBG binding capacity and concentration are changed under physiological and pathological conditions. It is better than FT 3 in the diagnosis of hypothyroidism. In the early stage of hyperthyroidism and follow-up, or low T 3 syndrome caused by certain diseases, combined with FT 3 and TSH measurement can improve the diagnostic compliance rate.
Reference range of normal free thyroxine
- Normal reference value of serum free thyroxine content: 12 22pmol / L