CPT® Code 84439

The CPT® Code 84439 refers to the laboratory test for free thyroxine, commonly known as T4. This test involves obtaining a blood sample to measure the levels of free thyroxine in the bloodstream. Thyroxine is a crucial hormone produced by the thyroid gland, and it plays a significant role in regulating various metabolic processes in the body. The measurement of free thyroxine is essential for assessing thyroid function, as it represents the fraction of thyroxine that is not bound to proteins and is available to enter cells and exert its effects. This test is particularly important in diagnosing thyroid disorders, including hyperthyroidism, where there is an excess of thyroid hormone, and hypothyroidism, where there is a deficiency. The free thyroxine test is considered to provide a more precise evaluation of thyroid function compared to total thyroxine tests, which measure both bound and unbound thyroxine. The methodology employed for this test is electrochemiluminescent immunoassay, a sensitive and specific technique that enhances the accuracy of the results.