Diagnosis of hyper- and hypothyroidism.
adv. Thyroid Panel
TSH, T3, T4, free T3, freeT4
T4 Total, Total thyroxine, serum
Total thyroxine is rarely measured, having been largely superseded by free thyroxine tests. Total thyroxine (Total T4) is generally elevated in hyperthyroidism and decreased in hypothyroidism. It is usually slightly elevated in pregnancy secondary to increased levels of thyroid binding globulin (TBG).
Total T4 is measured to see the bound and unbound levels of T4. The total T4 is less useful in cases where there could be protein abnormalities. The total T4 is less accurate due to the large amount of T4 that is bound. The total T3 is measured in clinical practice since the T3 has decreased amount that is bound as compared to T4.
Reference ranges depend on the method of analysis. Results should always be interpreted using the range from the laboratory that performed the test
Free T3, Serum
Evaluation of hyperthyroidism, thyrotoxicosis
Free T4, Serum
Confirming hyperthyroidism; Evaluation of thyroid function in patients with TBG alternations