Test Overview
Chemiluminescent Immunoassay
Thyroid function test, particularly useful in the diagnosis of T3 thyrotoxicosis and confirmation of hyperthyroidism. Needed in patients with clinical evidence for hyperthyroidism, in whom thyroid profile is normal or borderline.
80 - 175 ng/dL
* Reference ranges may change over time. Please refer to the original patient report when evaluating results.
Specimen may be stored at room temperature up to 8 hours. [12/05]
Influenced by state of nutrition and alterations in liver function due to TBG production. Serum T3 levels are increased during pregnancy and in women receiving oral contraceptives. Levels decreased by acute and chronic illness and by some drugs.
Test Details
4 hours
- Synthroid (Levothyroxine)
- Triiodothyronine
Specimen Requirements
Collect specimen in a red top or SST tube. Centrifuge, aliquot serum into a plastic vial and refrigerate up to 48 hours or freeze for longer storage.
Additional Information
Hyperproduction of T3 always occurs in hyperthyroidism. In addition, in approximately 5% of hyperthyroidism only T3 (and not T4) is elevated. This occurs in early hyperthyroid states and in hyperthyroid individuals in iodine deficient areas. Reduced levels of T3 are associated with compromised liver function, malnutrition and possibly with advancing age.