The Sensitive Serum TSH Test

 To detect thyroid problems, the most thorough and accurate test is the "sensitive serum TSH test," according to John T. Nicoloff, M.D., an endocrinologist and professor of medicine at the University of Southern California. "The sensitive serum TSH test is the gold standard of thyroid testing," he said. "It's simple and very sensitive, and can detect thyroid disease early."

TSH is thyroid stimulating hormone, produced by the pituitary gland. TSH stimulates the thyroid gland to produce T3 (triiodothyronine) and T4 (thyroxine) which regulate the metabolism of fat, protein, and sugar. Hypothyroidism results when T4 levels in the body are too low, and it occurs in two main forms: primary hypothyroidism and secondary hypothyroidism.

Different Causes, Same Symptoms

 If you have primary hypothyroidism, your thyroid itself malfunctions, whether from disease or an autoimmune condition. As a result, your thyroid can't produce enough T4, and you experience the fatigue, weight gain, and depression associated with low thyroid levels." With this form of hypothyroidism, your TSH levels would be abnormally high, as your pituitary gland tries to stimulate your thyroid to produce more T4.

With secondary hypothyroidism, one cause could be that your pituitary gland isn't producing enough TSH. In turn, your thyroid isn't producing enough T4. Your body's T4 levels are still low, but here the main culprit is your pituitary gland, not your thyroid gland. Your thyroid's problem is "secondary" to your pituitary's malfunction, but you feel the same symptoms.

In either case, the TSH test is useful, detecting either high or low levels of TSH and signaling your doctor to investigate further.

Screening Before Testing

The sensitive serum TSH test is "expensive, but the price is coming down," Dr. Nicoloff pointed out. (The test involves drawing a blood sample which is analyzed in a laboratory. Costs range from $45 to $75). He does not recommend routine TSH testing in women of menopausal age. The test should be done selectively after three main factors are considered:

1. Family History. "A person with a family history of thyroid disease is a potential candidate for the test," he said. "It's often hereditary."
2. Presence of an autoimmune disease such as vitiligo (skin discoloration), rheumatoid arthritis, or pernicious anemia. "Any of these conditions can be a hallmark of thyroid disease," he stated.
3. Enlarged thyroid or goiter. In a physical examination, you are asked to swallow. If your doctor feels an enlarged thyroid, Dr. Nicoloff said, "it's a good idea to do the [TSH test]."

Alternative Testing

 Other methods of testing thyroid levels are available, such as the "free T4" test, which measures the amount of T4 in your blood. But this test doesn't give the doctor enough information; it can show normal T4 levels, even if the body's production of TSH is still low. Dr. Nicoloff emphasized that the TSH level is the most important variable and described the sensitive serum TSH test as "the only one necessary."

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Osteoporosis Risk

 If you are diagnosed with hypothyroidism and put on medication, your doctor should monitor your dosage periodically.

Synthroid, a synthetic form of T4, is commonly prescribed to replace the body's missing thyroid hormone. If you take too much Synthroid, however, you could be at risk for osteoporosis. Too much thyroid hormone in your body, either from too much medicine or from hyperthyroidisim (in which the thyroid produces too much T4), can leach calcium from your bones. Dr. Nicoloff said the sensitive serum TSH test can also be used to regulate thyroid medication levels.

A natural form of thyroid contains both T3 and T4, and more closely resembles the body's natural production of thyroid hormones.

Thyroid is taken orally in tablet or capsule form. Dosages depend on individual symptoms, and must be carefully monitored.