This test is indicated if there is suspected hypothyroidism or a risk of hypothyroidism.
Immunometric assays are the most sensitive, specific and reliable tests with detection limits of 0.1-0.001 mU/L.
Radioimmunoassays have a detection limit of 1.0 mU/L are now rarely used.
Note that reference ranges may vary between laboratories.
Last reviewed 04/2022