T4 is produced by the thyroid gland and converted in body tissues into the more active hormone T3. Most circulating T4 is bound to proteins, with only a small free fraction biologically active. Total T4 measures both bound and free forms; free T4 isolates the active portion.
This test is ordered to evaluate suspected thyroid disorders, particularly when TSH is abnormal; monitor patients on thyroid hormone replacement or antithyroid medications; assess thyroid function during pregnancy; and investigate pituitary disorders that affect thyroid hormone production. T4 is often interpreted alongside TSH for the clearest picture. Sample type is serum.
We are CLIA certified, the highest level of Medical industry compliance and standards.
Book an appointment