T-3, FREE 0034429

A T3 test is used to assess thyroid function. It is ordered primarily to help diagnose hyperthyroidism and may be ordered to help monitor the status of a person with a known thyroid disorder. The T3 test is usually ordered following an abnormal TSH and T4 test. Either the total T3 or the free T3 may be ordered. Since most of the T3 is bound to protein, the total T3 can be affected by protein levels and protein binding ability, but the free T3 is not. T3 testing may be ordered along with thyroid antibodies to help diagnose Graves disease, an autoimmune disorder that is the most common cause of hyperthyroidism.