It is clear that individuals who present with signs and symptoms of thyrotoxi-cosis should have thyroid function tests carried out. However, there has been an ongoing debate about the role of screening in asymptomatic patients. In 1990, American Thyroid Association guidelines recommended against screening of asymptomatic patients, as it was unclear whether early diagnosis conferred any benefit (8). As recently as 1996, the U.S. Preventive Services Task Force recommended against TSH screening for asymptomatic adults (9). In 1998 the American College of Physicians issued guidelines recommending routine TSH screening for all women over age 50 (10). More recently, given the high prevalence of thyroid dysfunction in the general population, and the potentially serious consequences of undetected disease, the American Thyroid Association has advocated the screening of all adults aged 35 yr or over with serum TSH measurements every 5 yr (11). This approach has been found to be cost-effective, particularly in women, although only because of the detection of overt and subclinical hypothyroidism, which is more prevalent than thyrotoxicosis (12). We believe that this recommendation is somewhat arbitrary but that serum TSH testing should certainly be carried out in women over age 55 yr on a regular basis.
More frequent screening is indicated in patients with known risk factors such as the presence of a goiter, a history of type 1 diabetes mellitus, previous thyroid surgery or radiation, pernicious anemia, premature gray hair, vitiligo, or any previous history or family history of thyroid disease. Additionally, in any patient with an unexplained laboratory abnormality such as hypercholesterolemia, hyponatremia, anemia, hypercalcemia, or creatine kinase elevation serum TSH levels should be determined (11). Patients with new-onset atrial fibrillation should also be tested, since approximately 15% will be thyrotoxic (13,14). Patients should be evaluated for thyroid dysfunction before starting therapy with iodine-containing medications and then periodically while taking those medications.
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