What is a thyroid function test?
A thyroid function test is a test that measures the hormone level in the blood. As these hormones are produced by the thyroid gland, and affect nearly every organ in the body, the test eventually measures the function of the thyroid gland. The hormone varies, so does the test.
Tests to evaluate the thyroid function include:
- TSH test: checks the level of TSH (the hormone that tells how much T3 and T4 to make). A change in the TSH level could indicate a thyroid problem. So, it’s common to take only TSH test at first. When the result is abnormal, the following tests are taken.
- T4 test: measures the level of T4 (thyroxine), the hormone that secreted by the thyroid gland.
- T3 test: measures the level of T3 (triiodothyronine), the hormone converted from T4.
- Free T4 test: measures the level of “free” T4, which are unbound to the proteins in the blood and do enter various tissues to function. This is the most important one to evaluate the function of the thyroid gland.
- Antibody test: helps diagnose the cause of the thyroid problem.
Keywords: thyroid function test