. TT4 is used to evaluate the function of the thyroid gland, which regulates metabolism, energy production, and overall growth and development.
. TT4 measures the total amount of T4 hormone in the blood, including both bound and free forms. levels can fluctuate with physiological and pathological changes in TBG concentration.
. TT4, along with other TFT, is used to diagnose thyroid dysfunction (e.g., hyperthyroidism, hypothyroidism), to monitor treatment for thyroid disorders (especially in those taking thyroid hormone replacement or anti-thyroid medications), to evaluate conditions such as Graves' disease, Hashimoto's thyroiditis, or thyroid nodules, and to detect non-thyroidal illness (conditions affecting thyroid hormone levels independently of thyroid function).