Free Thyroxine (FT4)
Electrochemiluminescence Immunoassay (ECLIA)
Tuesday & Friday
One 6mL RT (Min: 4mL RT)
1 mL refrigerated serum (Min: 0.5 mL)
Stored at 2 - 8°C until used; Stable if frozen at - 20°C
Do not use heat-inactivated samples.
0.80 – 2.0 ng/dL
The thyroid hormone thyroxine (T4) is a physiologically active thyroid hormone and the principle secretory product of the thyroid gland, which has an effect on general metabolism. The major fraction of the total thyroxine is bound to transport proteins (TBG, prealbumin and albumin). The free thyroxine (FT4) moiety is the physiologically active thyroxine component. The determination of FT4 is an important test in the clinical diagnosis and treatment of thyroid disorders.
The determination of free T4 has the advantage of being independent of changes in the concentrations and affinity of the thyroid hormone binding proteins (primarily TBG). The estimation of FT4 usually renders an additional binding protein ratio test (THBR) unnecessary.