Thyroid Hormone Tests
T3 (Triiodothyronine) Test, T4 (Thyroxine) Test, Thyroxine (T4) Test, Triiodothyronine (T3) Test
What To Think About
- Other blood tests are often used to check how well the thyroid gland is working.
- Thyroid-stimulating hormone (TSH) test measures the amount of TSH in the blood and is considered the most reliable way to find a thyroid problem. If the TSH test is abnormal, other thyroid hormone tests such as a T3 or T4 may be done. For more information, see the medical test Thyroid-Stimulating Hormone.
- Thyroid antibodies test. This test measures the presence of antibodies against thyroid tissue. Antibodies may mean that you have an autoimmune disease such as Hashimoto's thyroiditis or Graves' disease.
- Thyroxine-binding globulin (TBG) test. TBG is an important protein in the blood that carries the thyroid hormones T3 and T4. TBG testing is not done very often.
- Other tests used to investigate problems with the thyroid gland include thyroid scan, ultrasound, or biopsy. For more information, see the medical tests Thyroid Scan and Radioactive Iodine Uptake Test, Thyroid Ultrasound and Parathyroid Ultrasound, and Thyroid Biopsy.
- Because false-positive results can occur when testing a newborn for congenital hypothyroidism, the thyroid hormone tests may be repeated a few days after initial testing. If the results are still abnormal and congenital hypothyroidism is suspected, additional testing is done.
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| Author: | Caroline Rea, RN, BS, MS | Last Updated: December 3, 2007 |
| Medical Review: | Caroline S. Rhoads, MD - Internal Medicine David C.W. Lau, MD, PhD, FRCPC - Endocrinology & Metabolism | |
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| Topic Contents | |
| Test Overview | |
| Why It Is Done | |
| How To Prepare | |
| How It Is Done | |
| How It Feels | |
| Risks | |
| Results | |
| What Affects the Test | |
 | What To Think About |
| References | |
| Credits | |