Thyroid function tests
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: TFTs
Overview
Thyroid function tests (TFTs) is a collective term for blood tests used to check the function of the thyroid.
A TFT panel typically includes thyroid-stimulating hormone (TSH, thyrotropin) and thyroxine (T4), and triiodothyronine (T3) depending on local laboratory policy.
TFTs may be requested if a patient is thought to suffer from hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid), or to monitor the effectiveness of either thyroid-suppression or hormone replacement therapy. It is also requested routinely in conditions linked to thyroid disease, such as atrial fibrillation.
Thyroid function tests
The normal adult reference range for serum TSH is 0.4-4.5 mIU/L. A high TSH level may indicate hypothyroidism. If the results indicate high TSH levels, a second confirmatory sample including TSH and free T4 levels should be tested prior to starting treatment. TSH should not be measured in isolation in patients with suspected hypothalamic-pituitary disease; the measurement of free T4 is essential. Conditions other than thyroid disease should be considered when TSH levels are abnormal such as physiological changes associated with pregnancy, severe nonthyroidal illness, and medication use (including amiodarone, lithium, dopamine and glucocorticoids).