A free T3 test measures Free Triiodothyronine (T3) level in the blood.
T3 levels are regulated by the feedback system that the body uses to maintain stable amounts of thyroid hormones in the blood. Most of the hormone produced by the thyroid is T4. This hormone is relatively inactive but is converted into the much more active T3 in the liver and other tissues.
T3 and T4 are two hormones that work together to regulate the body’s metabolism. These hormones play an essential role in controlling
the body’s weight, body temperature, muscle strength, and nervous system.
Bound T3: which attaches to protein.
Free T3: which does not attach to anything (i.e., its free).
Both may be used to check T3 levels.
Since most T3 is bound to protein, the total T3 can be affected by protein levels in the body. Free T3 is not affected by protein levels.
A T3 test is frequently requested to diagnose hyperthyroidism, a condition in which the body produces too much thyroid hormone.
This is a single-marker test measuring free T3. It is used to evaluate thyroid function.
