Thyroid Testing: Part 1

T3, or triiodothyronine, is the second hormone produced by the thyroid. The body may produce more T4,but T3 is the more active of the two thyroid hormones.

(Please note that certain conditions such as pregnancy can increase the level of the TBGs which carry T3 and may artificially raise the level of the total T3.)

In that case, the free T3 test may need to be run. Since less than 1% of T3 is free, this test can be very sensitive.

If your test results are low for the T3 or Free T3 test, it may indicate hypothyroidism. T3 is considered normal in the 80 to 220 range whereas Free T3 is normal from 2.3 to 4.2.

Usually, by this point, your physician will be able to make a diagnosis of hypothyroidism. If not, you do have other options. We will discuss those in another article.

Sources Include: Shomon, Mary J. How to Tell If You Are Hypothyroid. Retrieved on July 2, 2004 from the World Wide Web: http://thyroid.about.com/library/howto/h...

Shomon, Mary J. Key Thyroid Function Tests: Laboratory Values and Interpretation. Retrieved on July 2, 2004 from the World Wide Web: http://thyroid.about.com/cs/newsinfo/l/b...

Healthwise, Inc. Health Guide A-Z: Thyroid Hormone Tests. Retrieved on July 2, 2004 from the World Wide Web: http://my.webmd.com/hw/womens_conditions...

Endocrine Web and the Norman Endocrine Surgery Clinic. Common Tests to Examine Thyroid Gland Function. Retrieved on July 2, 2004 from the World Wide Web: http://www.endocrineweb.com/tests.html

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