What is free thyroid 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 FTI in thyroid?

FTI =thyroxine (T4)/thyroid binding capacity. The FTI is a normalized determination that remains relatively constant in healthy individuals and compensates for abnormal levels of binding proteins. Hyperthyroidism causes increased FTI, and hypothyroidism causes decreased values.

What is T3 uptake and FTI?

The FTI is obtained by multiplying the (Total T4) times (T3 Uptake) to obtain an index. The FTI is considered a more reliable indicator of thyroid status in the presence of abnormalities in plasma protein binding. It is elevated in hyperthyroidism and depressed in hypothyroidism.

How is free T4 measured?

T4 is measured by taking a blood sample. A low T4 test result may indicate an underactive thyroid gland or problems with its stimulation by the pituitary gland. A high level of T4 may be a sign of an overactive thyroid, called hyperthyroidism.

How do you calculate FTI?

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.

What does low FTI mean?

A low TSH and low FT4 or FTI indicates hypothyroidism due to a problem involving the pituitary gland. A low TSH with an elevated FT4 or FTI is found in individuals who have hyperthyroidism. T3 TESTS. T3 tests are often useful to diagnosis hyperthyroidism or to determine the severity of the hyperthyroidism.

What is normal FTI?

Reference range for T-uptake ratio is 0.7–1.2 and for FTI is 6–11.00 μg/dL.

What is the difference between T3 and free T3?

The T3 test is used to help diagnose thyroid problems, such as hyperthyroidism. Hyperthyroidism means the thyroid gland makes too many thyroid hormones. T3 has 2 forms: bound and free. Bound T3 is attached to a protein and free T3 is not attached to anything.

What is the normal range for free T3?

Normal Results The range for normal values are: Total T3 — 60 to 180 nanograms per deciliter (ng/dL), or 0.9 to 2.8 nanomoles per liter (nmol/L) Free T3 — 130 to 450 picgrams per deciliter (pg/dL), or 2.0 to 7.0 picomoles per liter (pmol/L)

What is the difference between free T4 and free T4 index?

Free T4 is usually measured 2 ways: Free T4, with normal ranges determined by the testing method the lab uses. Free T4 index, a formula that includes total T4 and a measurement called thyroid hormone-binding index. The normal range for the free T index is 1.1 to 4.3 mcg/dL.

What is low free thyroxine index?

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.

What is an FTI?

FTI is any return or return information received from the IRS or any secondary source which is protected by the confidentiality provisions of Internal Revenue Code section 6103.