Free Thyroxine Index Formula. Largely replaced by free t4 ( free thyroxine) The free thyroxine index (fti) is determined by the following calculation:
The fti is a normalized determination that remains relatively constant in healthy individuals and compensates for abnormal levels of binding proteins. Fti = thyroxine (t4)/thyroid binding capacity. I weigh 135 pounds, which is equal to 61.2 kg.
Reference range 2.0 to 4.4 pg/ml.
This with normal ranges, is identifiable by the testing method which the lab uses mostly; Fti means the test result was calculated using a formula that compares total t4 and some estimation of the level of thyroid hormone proteins. Fti = thyroxine (t4) / thyroid binding capacity fti increases could be caused by hyperthyroidism whilst decreased fti could be attributed to hypothyroidism. The fti is a normalized determination that remains relatively constant in healthy individuals and compensates for abnormal levels of binding proteins.
