T3 and T4 Thyroid Hormone Test
|Why is this test done?||Thyroid hormone levels are measured to diagnose or monitor thyroid disorders.|
|How to prepare:||There are no dietary restrictions prior to this test.|
|Associated Tests:||In addition to thyroid hormones, other tests done to evaluate the thyroid function include TSH (thyroid-stimulating hormone) , thyroglobulin and anti-thyroid antibodies.|
Thyroid hormones include the T4 (Thyroxine) and T3 (Triiodothyronine) hormones. These hormones are found under two states in the blood: either free (active) or protein-bound (which constitutes stores). TSH (thyroid-stimulating hormone) and the amount of available iodine closely regulate the production of these hormones by the thyroid gland. The thyroid hormones play several roles in the body, including sugar and lipid metabolism as well as bone and brain development.
What does an abnormal test result mean?
If the result is too high
This indicates that the thyroid gland works too hard. This is called hyperthyroidism. A too high dose of replacement hormones can also give high results.
If the result is too low
This indicates that the thyroid gland does not works hard enough. This is called hypothyroidism.
Factors that can affect the result of the test
Certain medical tests (radioisotopic tests) and pregnancy can affect results. Certain drugs can also affect results, they include:
What you need to know before the test
Before going for blood tests, a procedure or other exam, it is best to always bring a list of all the drugs you take (prescription, OTC and natural health products). Unless told otherwise, you should take your medication as usual on the day of the test. When in doubt, ask your pharmacist for more information.
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The patient information leaflets are provided by Vigilance Santé Inc. This content is for information purposes only and does not in any manner whatsoever replace the opinion or advice of your health care professional. Always consult a health care professional before making a decision about your medication or treatment.