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Detecting thyroid problems.

Are there any blood tests for thyroid problems other than the standard ones?

Donald Willson

Virginia Beach, Virginia

Yes, but less common tests can help only very specific situations, such as when patients are critically ill, have thyroid eye disease, thyroid cancer, or are pregnant.

"The standard blood tests for thyroid problems are TSH (thyroid stimulating hormone), estimates of free T4 (thyroxine or tetraiodothyronine), total and estimates of free T3 (triiodothyronine), and thyroid antibodies; others are usually not necessary," says Dr. Jeffrey Gather, chief of endocrinology at Harvard Vanguard Medical Associates.

TSH regulates the release of T3 and T4, and blood tests of the master hormone can signal potential thyroid problems before symptoms appear.

"Thyroid antibody tests are of some benefit when TSH levels are borderline," Dr. Garber continues. "Estimates of free T4 are particularly helpful when one's thyroid status is in flux after changing thyroid medication, thyroid surgery, or radioactive iodine treatment. Total T3 and estimates of free T3 are used to diagnose overactive thyroid when T4 measures are normal. T3 testing, however, has no proven role in the diagnosis or treatment of hypothyroidism.

"Less common tests include those for TSH receptor antibodies to diagnose Graves' disease during pregnancy (when radioactive iodine tests may not be performed) or to diagnose thyroid eye disease. Reverse T3 levels can help distinguish low thyroid hormone levels due to hypothyroidism from low thyroid hormone levels due to critical illness. Tests for alpha subunits (a component of TSH) are employed to diagnose rare pituitary disorders that cause an overactive thyroid. Determinations of thyroglobulin (a protein made by thyroid cells) and thyrocalcitonin (a hormone made by cells within the thyroid that don't produce T3 and T4) are useful in the diagnosis and treatment of thyroid cancer."

Dr. Garber adds that people often ask about other tests when their thyroid treatment doesn't relieve symptoms such as depression or fatigue.

"It's important to note that treating symptoms with higher than standard thyroid hormone [doses] increases the risk of side effects as well as the chance of overlooking other important conditions," explains the endocrinologist.

"For example, hypothyroidism can masquerade as depression, but depression can masquerade as hypothyroidism. Likewise, there are many reasons for feeling tired besides our thyroid."

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Title Annotation:Medical Mailbox
Publication:Saturday Evening Post
Geographic Code:1USA
Date:Nov 1, 2010
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