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.
T3 uptake is also known as T3 Resin Uptake (T3RU) or Thyroid Uptake. It estimates how much thyroid hormone-binding proteins are available in the blood through a calculation based on levels of T3 or T4 added to a person's blood specimen.
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.
A TSH test is a lab test that measures the amount of thyroid stimulating hormone (TSH) in your blood. TSH is produced by the pituitary gland. It tells the thyroid gland to make and release thyroid hormones into the blood.