What is considered a low thyroid level?

Written by j.d. chi
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The thyroid is the gland in your body that regulates your metabolism. It produces two key hormones: T3 and T4. Figuring out if you are producing the right amount of thyroid hormones requires multiple tests to be run---and analysed---in concert. Critical to determining if your thyroid hormones are normal is being tested for the T4 or T3 hormone along with being tested for TSH (thyroid stimulating hormone). Testing for thyroid levels helps a physician determine if a patient has an over- or under-active thyroid, thyroid cancer or a pituitary gland issue.

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T4 Reading

You can be tested for the level of T4 hormone in your blood. You may be tested using a Total T4 test or a Free T4 test. Using a Total T4 test, a number between 4.5 and 12.5 is considered normal. If your test results are below 4.5, that may indicate an under-active thyroid. If the numbers are above 12.5, it may indicate an overactive thyroid. Using the Free T4 test, the normal range is .7-2.0. If your test results are below .7, then you may have an under-active thyroid. If your test results are above 2.0, you may have an overactive thyroid. This test should be combined with the TSH and T3 tests to get a clear picture of the condition.

T3 Reading

You may be tested using a Total T3 or Free T3 test. Using the Total T3 test, the normal range is 60 to 181. If your test results are below 60, it may indicate an under-active thyroid. If your results are above 186, it may indicate an overactive thyroid. The Free T3 test uses numbers between 230 to 420. If your test results are below 230, it may indicate an under-active thyroid. If the results are above 420, it may indicate an overactive thyroid. This test should be combined with the TSH and T4 tests to get a clear picture of the condition.

TSH Reading

A TSH test (short for thyroid stimulating hormone) measures the amount of TSH produced by the pituitary glands. The normal range for TSH is between .5 and 5.0. However, clinical tests done in the early 2000s showed that some people with readings at 5.0 level actually had under-active thyroids. Because of this, physicians use a scale of .3 to 3.0 when determining the normal range. It is important to note, as above, the TSH test is not conclusive enough to be considered alone and should be combined with tests for T4 and/or T3 levels.

Making Sense of Test Results

Because production of T4, T3 or TSH alone is not enough to determine a specific thyroid issue, it is critical these tests be combined. The pituitary gland produces TSH and may register at high levels if no or not enough T4 is being produced. Conversely, it may register at low levels if too much T4 is being produced. Therefore, these results must be considered together. In addition, the level of TSH in the blood system may be an indication of a pituitary gland problem rather than a thyroid problem.

Hypothyroidism

If you are diagnosed with an under-active thyroid or hypothyroidism, the thyroid does not produce enough T3 and/or T4 hormone, and you will be left feeling sluggish, will be likely to gain weight and may feel unmotivated. Treatment for an under-active thyroid is drug therapy; a lifelong regimen of thyroid-replacement hormones. The most common brand-name medications are Synthroid and Levoxyl, both which are tiny pills taken daily. There are no side effects with either. Once a patient is diagnosed as hypothyroid, the physician will begin experimenting with varying doses of the new medication. It can take up to a year to find the right dosage.

Endocrinologist

A specialist in treating patients with thyroid issues is called an endocrinologist. These physicians specialise in treating endocrine issues, which are issues relating to hormone-producing glands.

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