CPT® Code 84481

The CPT® Code 84481 refers to the laboratory test for free triiodothyronine (T3), a crucial hormone produced by the thyroid gland. This test specifically measures the levels of free T3 in the blood, which is the active form of the hormone that plays a significant role in regulating various metabolic processes within the body, including body temperature, growth, and heart rate. T3 is primarily derived from the conversion of thyroxine (T4) and is predominantly found in two forms in the bloodstream: approximately 95% of T3 is bound to proteins, rendering it inactive, while the remaining 5% exists as free T3, which is biologically active and can exert its effects on target tissues. The measurement of free T3 is essential for assessing thyroid function, particularly in diagnosing conditions such as hyperthyroidism, where the thyroid gland is overactive. Additionally, this test is instrumental in monitoring patients who have been diagnosed with thyroid disorders, providing valuable insights into their treatment efficacy and overall thyroid health. The testing process for free T3 involves the use of electrochemiluminescent immunoassay, a sensitive and specific method that allows for accurate quantification of the hormone in the blood. This test is distinct from the total T3 test (CPT® Code 84480), which measures both bound and free T3, and from the reverse T3 test (CPT® Code 84482), which evaluates an inactive form of T3 that may indicate thyroid dysfunction when present in elevated levels.