What is free T4 index?
The free T4 index (FTI) is a blood test used to diagnose thyroid disorders. T4, also called thyroxine, is a thyroid hormone. The test measures how much of it is in your blood to help determine whether your thyroid gland is underactive (hypothyroidism) or overactive (hyperthyroidism).
What is the difference between free T4 and free T4 index?
A Free T4 measures what is not bound and able to enter and affect the body tissues. Tests measuring free T4 – either a free T4 (FT4) or free T4 index (FTI) – more accurately reflect how the thyroid gland is functioning when checked with a TSH.
What percentage of T4 is free?
A minimal amount, about 0.02%, of T4 in the serum is free, or unbound. For T3, approximately 80% is bound to TBG, 5% to TTR, and 15% to albumin and lipoproteins.
What is FTI in thyroid test?
Free thyroxine (T4) can be measured directly (FT4) or calculated as the free thyroxine index (FTI). The FTI tells how much free T4 is present compared to bound T4. The FTI can help tell if abnormal amounts of T4 are present because of abnormal amounts of thyroxine-binding globulin.
Which is more important TSH or free T4?
Because T4 is converted into another thyroid hormone called T3 (triiodothyronine), free T4 is the more important hormone to measure. Any changes show up in T4 first.
Is 1.4 free T4 normal?
The normal range for free T 4 in adults is 0.8 to 1.8 nanograms per deciliter (ng/dL). A level of free T 4 that is higher than normal could mean you have an overactive thyroid. Conditions associated with hyperthyroidism include Graves disease, an autoimmune disorder.
How do you calculate free T4 from total T4?
Free thyroxine index is calculated by dividing the total T4 by the TBI value (T-uptake ratio). Interassay precision (CV) is <5%. Reference range for T-uptake ratio is 0.7–1.2 and for FTI is 6–11.00 μg/dL.
How do you calculate FTI?
FTI = Total T4 x (%T-Uptake/100)
Is T3 more important than T4?
Because T4 is converted into another thyroid hormone called T3 (triiodothyronine), free T4 is the more important hormone to measure.
T4, Free. Optimal Result: 0.82 – 1.77 ng/dL, or 10.55 – 22.78 pmol/L. Thyroxine or T4 is a hormone produced by the thyroid gland. The term “free T4” means measured T4 that is not bound to proteins in the blood. T4 is about one-tenth as potent as T3 in humans.
What is free T4 levels mean?
What is free T4 levels mean? Free T4 results are typically evaluated with other thyroid testing results (i.e., TSH and sometimes total or free T3). In general, high free T4 results may indicate an overactive thyroid gland (hyperthyroidism), and low free T4 results may indicate an underactive thyroid gland (hypothyroidism).
What is T4 index?
The free T4 index includes a formula that compares free and bound T4. High levels of any of these tests (total T4, free T4, or free T4 index) may indicate an overactive thyroid, also known as hyperthyroidism. Low levels of any of these tests (total T4, free T4, or free T4 index) may indicate an underactive thyroid, also known as hypothyroidism.