Triiodothyronine (T3), Free

Overview:

T3 is the more active of the thyroid hormones, and most of it is made by converting T4 within tissues. Measuring the free portion gives the amount actually available to act, without the distortion that carrier protein changes cause in a total measurement. Free T3 is most useful in assessing an overactive thyroid, where it can be raised while free T4 remains normal, a pattern sometimes called T3 toxicosis. It is less useful in underactive thyroid, since conversion usually maintains T3 until the condition is advanced. Levels fall during serious illness in people with normal thyroid function.

Categories:

Thyroid

Biomarkers:

1 biomarker