Screening for Thyroid Disease: Recommendation Statement

Summary of the Recommendation

The U.S. Preventive Services Task Force (USPSTF) concludes the evidence is insufficient to recommend for or against routine screening for thyroid disease in adults. This is a grade I recommendation. (See Appendix Table 1 for a description of the USPSTF classification of recommendations.)

The USPSTF found fair evidence that the thyroid-stimulating hormone (TSH) test can detect subclinical thyroid disease in people without symptoms of thyroid dysfunction but poor evidence that treatment improves clinically important outcomes in adults with screen-detected thyroid disease. (See Appendix Table 2 for a description of the USPSTF classification of levels of evidence.) Although the yield of screening is greater in certain high-risk groups (for example, postpartum women, people with Down syndrome, and the elderly), the USPSTF found poor evidence that screening these groups leads to clinically important benefits. There is the potential for harm caused by false-positive screening tests; however, the magnitude of harm is not known. There is good evidence that overtreatment with levothyroxine occurs in a substantial proportion of patients, but the long-term harmful effects of overtreatment are not known. As a result, the USPSTF could not determine the balance of benefits and harms of screening asymptomatic adults for thyroid disease.

Clinical Considerations

Subclinical thyroid dysfunction is defined as an abnormal biochemical measurement of thyroid hormones without any specific clinical signs or symptoms of thyroid disease and no history of thyroid dysfunction or therapy. This includes individuals who have mildly elevated TSH and normal thyroxine (T₄) and triiodothyronine (T₃) levels (subclinical hypothyroidism) or low TSH and normal T₄ and T₃ levels (subclinical hyperthyroidism). Individuals with symptoms of thyroid dysfunction, or those with a history of thyroid disease or treatment, are excluded from this definition and are not the subject of these recommendations.

When used to confirm suspected thyroid disease in patients referred to a specialty endocrine clinic, TSH has a high sensitivity (98%) and specificity (92%). When used for screening primary care populations, the positive predictive value of TSH in detecting thyroid disease is low; furthermore, the interpretation of a positive test result is often complicated by an underlying illness or by frailty of the individual. In general, values for serum TSH level below 0.1 mU/L are considered low and values above 6.5 mU/L are considered elevated.

Clinicians should be aware of subtle signs of thyroid dysfunction, particularly among those at high risk. People at higher risk for thyroid dysfunction include the elderly, postpartum women, those with high levels of radiation exposure (>20 mGy), and patients with Down syndrome. Evaluating for symptoms of hypothyroidism is difficult in patients with Down syndrome because some symptoms and signs (for example, slow speech, thick tongue, and slow mentation) are typical findings in both conditions.

Subclinical hyperthyroidism has been associated with atrial fibrillation; dementia; and, less clearly, osteoporosis. However, progression from subclinical to clinical disease in patients without a history of thyroid disease is not clearly established.

Subclinical hypothyroidism is associated with poor obstetric outcomes and poor cognitive development in children. Evidence for dyslipidemia, atherosclerosis, and decreased quality of life in adults with subclinical hypothyroidism in the general population is inconsistent and less convincing.

Recommendations of Other Groups

The American Thyroid Association recommends measuring thyroid function in all adults beginning at age 35 years and every 5 years thereafter, noting that more frequent screening may be appropriate in high-risk or symptomatic individuals (1). The Canadian Task Force on the Periodic Health Examination recommends maintaining a high index of clinical suspicion for nonspecific symptoms consistent with hypothyroidism when examining perimenopausal and postmenopausal women (2). The American College of Physicians recommends screening women older than age 50 years with 1 or more general symptoms that could be caused by thyroid disease (3). The American Association of Clinical Endocrinologists recommends TSH measurement in women of childbearing age before pregnancy or during the first trimester (4). The American College of Obstetricians and Gynecologists recommends that physicians be aware of the symptoms and risk factors for postpartum thyroid dysfunction and evaluate patients when indicated (5). The American Academy of Family Physicians recommends against routine thyroid screening in asymptomatic patients younger than age 60 years (6).