Free Thyroxine Index Vs Free T4. If your results appear as high total t4 or a high free t4 index, it indicates you might be experiencing from hyperthyroidism. The correlations of the total t3, free t3, and free t3 index with, respectively, the total t4, free t4, and free t4 index were much lower, though still statistically significant.
The free t3 index is clinically useful because serum total t3 may sometimes be misleading. Free thyroxine comprises a small fraction of total thyroxine. Free thyroxine is often more useful than total thyroxine in assessing thyroid function.
What you really need to get out of all of this is the fact that your free t4 levels do not necessarily need to be in some magical optimal range for you to feel good.
The free thyroxine index (ft 4 i) is the product of the measured t 4 level and the triiodothyronine uptake (t 3 u). In most cases, free thyroxine (also known as free t4) is good indicator of thyroid function, along with tsh and other measures. Fti = thyroxine (t4) / thyroid binding capacity fti increases could be caused by hyperthyroidism whilst decreased fti could be attributed to hypothyroidism. Tsh and/or trhtsh responsiveness are high.
