The symptoms of thyroid disease can be masked in older women because they resemble signs of aging. The medical group says a simple blood test can help detect the disease.
Mark Helfand, who helped do research for the guidelines, said thyroid disease can be overlooked because doctors often are focusing on other health problems.
``If you are 68 or 70 and if you have high blood pressure, you talk about blood pressure,'' said Helfand, an internal medicine and critical-care specialist in Portland, Ore. ``You might have dry skin and fatigue, but that may be attributed to old age. . . . So I think it is unsuspected.''
Among women over 50, the medical group estimates that one out of every 71 has symptomatic thyroid disease that should be treated. Women over 50 are considered most at risk for the disease.
In all, about 11 million Americans have hypothyroidism, which involves the gland's producing too little thyroid hormone. Less common is hyperthyroidism - when the gland makes excessive hormone. It affects about two million Americans, mostly women between the ages of 20 and 40.
Hypothyroidism can be easily treated with a daily pill containing synthetic thyroid hormone. Hyperthyroidism is often treated with radioactive iodine, surgery or pills that block hormone formation.
Until this summer, the American College of Physicians, which develops medical guidelines for many illnesses, had not recommended routine screening and instead suggested the test only if people had obvious symptoms of thyroid disease.
Dr. John R. Feussner, who was involved in approving the new guidelines, said research has made it clear that early detection benefits patients who are showing symptoms, but don't know they have the disease.
The guidelines do not say whether to treat patients who have borderline abnormal tests, but don't have symptoms.
The screening involves a blood test to check the level of a pituitary hormone called thyroid-stimulating hormone (TSH). The pituitary hormone is responsible for regulating the thyroid gland. If the pituitary gland is pumping out too much hormone, it indicates the thyroid gland is not producing enough of its own hormone.
If the initial test suggests the thyroid gland may be out of whack, a follow-up blood test will be ordered.
Feussner said it was unclear how often to test someone with normal hormone levels.
``The answer is you should probably have it at least once when you turn 50,'' he said. ``It is not the kind of thing you have to have done every year.''