T4 (Thyroxine), Total
This test measures the amount of thyroxine, or T4, in the blood. T4 is one of two major hormones produced by the thyroid gland. The total T4 test is used to help diagnose hyperthyroidism and hypothyroidism. It is a useful test but can be affected by the amount of protein available in the blood to bind to the hormone.
Free T4 Index (T7)
FTI stands for the Free Thyroxine Index and is also sometimes referred to as T7. It is a calculated value determined from the T3 uptake test and total T4 test and provides an estimate of the level of free T4 in the blood.