Thyroid-Stimulating Hormone (TSH) Test

Experts estimate that about 14 million Americans have problems with their thyroid gland -- a small gland, measuring about two inches across, that lies just under the skin near the trachea (windpipe) in the neck. It secretes a hormone, thyroxine, that helps regulate growth, metabolism, digestion and body temperature. Many thyroid problems go undetected, even though screening is as simple as taking a blood test.

Who needs it The American College of Obstetricians and Gynecologists recommends that women age 65 and older have TSH tests every three to five years. Experts also recommend that men age 65 and older get tested regularly.

How it's done For 24 hours prior to the test, you'll be asked to avoid drugs that can affect the results, including aspirin, corticosteroids and iodine-containing drugs and vitamins. Blood is drawn and sent to a lab to check levels of thyroid-stimulating hormone (TSH).

What the results mean Normal levels of TSH are 0.5 to 5 milligrams per deciliter (mg/dl). Lower levels may indicate hypothyroidism, which can cause such symptoms as fatigue, sensitivity to the cold, weight gain, and constipation. If you have hypothyroidism, your doctor will probably prescribe a thyroid replacement drug -- a synthetic version of the hormone your body produces. High TSH levels, which are less common, may indicate hyperthyroidism, which can cause symptoms such as a fast heartbeat, weight loss, and dizziness. Graves' disease is the most common cause of hyperthyroidism. Treatment may involve antithyroid medicines, radioactive iodine treatment, or surgery to remove all or part of the thyroid gland.

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