Thyroid function tests are common procedures performed to determine how well the thyroid is functioning. Some of the most common thyroid function tests include the following:
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Blood tests. To measure the level of thyroid-stimulating hormone (TSH) in the blood which helps determine thyroid function. High levels of the hormone indicate an underactive thyroid. In addition, a blood test can measure levels of hormones thyroxine (T4) and triiodothyronine (T3), and to measure a protein called thyroglobulin.
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Ultrasound exam of the thyroid gland. To detect signs of abnormal enlargement, or nodules, on the thyroid, and to guide biopsies of concerning nodules. (An ultrasound scan is a diagnostic technique that uses high-frequency sound waves to create an image of the internal organs.)
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Thyroid scans using radioactive iodine or technetium (a radioactive metallic element). To help determine the cause of abnormal thyroid function. This is important in deciding whether a person will need a total thyroidectomy or partial thyroidectomy.
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Functional stimulation tests. Tests that help differentiate whether the problem is due to the pituitary gland, the hypothalamus, or the thyroid gland. One such test includes injecting thyrotropin-releasing hormone (produced by the hypothalamus) and measuring the pituitary's response.
