How Is Hypothyroidism Diagnosed?
If you suspect you have hypothyroidism, speak with your health care provider. Accurate diagnosis depends on a variety of observations and measures. When you are being evaluated for hypothyroidism, you can expect your health care provider to:
The thyroid stimulating hormone (TSH) test is the primary test for hypothyroidism. It measures how much thyroxine (or T4) the thyroid gland is being asked to make. In people with hypothyroidism, the thyroid is unable to produce enough of this hormone. With normal thyroid function, TSH levels range from 0.4 to 4.0 mIU/L (mIU/L stands for milli-international units per liter).
The Free T4 (FT4) and the Free T4 Index (FTI) tests are often used as secondary tests to confirm the results of the TSH test. They check how much T4 is in your blood and available for your body to use. There is just 1% to 2% of FT4 with normal thyroid function and even less than that in people with hypothyroidism.
Combining the TSH test with the FT4 or FTI test can accurately determine how your thyroid gland is functioning and if you have hypothyroidism.
This is not a comprehensive list of diagnostic tests your physician may select.
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