Synonyms: T4, Total; Tetraiodothyronine

Why It Is Done

This test is used to evaluate thyroid function and screen for hyperthyroidism or hypothyroidism. Shows effectiveness of medications to treat thyroid disease. Used to diagnose T4 toxicosis.

Test Overview

Total thyroxine (T4). Thyroxine is a hormone produced by the thyroid and is responsible for your metabolism. .Most of the thyroxine (T4) in the blood is attached to a protein called the thyroxine-binding globulin. Less than 1% of the T4 is unattached. A total T4 blood test measures both bound and free thyroxine. Free thyroxine affects tissue function in the body, but bound thyroxine does not

How To Prepare

No special preparation required