Mark Helfand, MD, MPH
Adapted with permission from Medicare Coverage of Routine Screening for Thyroid Dysfunction (Washington, DC: National Academies Pr; 2003) by the National Academy of Sciences, courtesy of the National Academies Press, Washington, DC.
Acknowledgments: The author thanks Robert Utiger, Marc Stone, Doug Bauer, Steven Teutsch, and David Atkins for their comments on the report on which this article is based.
Grant Support: By the Agency for Healthcare Research and Quality, Contract #290-97-0018, Task Order Number 2. Technical support was provided by the USPSTF.
Potential Financial Conflicts of Interest: None disclosed.
Requests for Single Reprints: Mark Helfand, MD, MPH, Oregon Health & Science University, Evidence-based Practice Center, Portland, OR 97239.
Subclinical thyroid dysfunction is a risk factor for developing symptomatic thyroid disease. Advocates of screening argue that early treatment can prevent serious morbidity in individuals who are found to have laboratory evidence of subclinical thyroid dysfunction.
This article focuses on whether it is useful to order a thyroid function test for patients who have no history of thyroid disease and have few or no signs or symptoms of thyroid dysfunction.
A MEDLINE search, supplemented by searches of EMBASE and the Cochrane Library, reference lists, and a local database of thyroid-related articles.
Controlled treatment studies that used thyroid-stimulating hormone (TSH) levels as an inclusion criterion and reported quality of life, symptoms, or lipid level outcomes were selected. Observational studies of the prevalence, progression, and consequences of subclinical thyroid dysfunction were also reviewed.
The quality of each trial was assessed by using preset criteria, and information about setting, patients, interventions, and outcomes was abstracted.
The prevalence of unsuspected thyroid disease is lowest in men and highest in older women. Evidence regarding the efficacy of treatment in patients found by screening to have subclinical thyroid dysfunction is inconclusive. No trials of treatment of subclinical hyperthyroidism have been done. Several small, randomized trials of treatment of subclinical hypothyroidism have been done, but the results are inconclusive except in patients who have a history of treatment of Graves disease, a subgroup that is not a target of screening in the general population. Data on the adverse effects of broader use of l-thyroxine are sparse.
It is uncertain whether treatment will improve quality of life in otherwise healthy patients who have abnormal TSH levels and normal free thyroxine levels.
Table 1. Classification of Thyroid Dysfunction
Table 2. Quality of Randomized Trials of Thyroxine Replacement Therapy
Table 3. Description and Results of Randomized Trials of Thyroxine Replacement Therapy
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Helfand M. Screening for Subclinical Thyroid Dysfunction in Nonpregnant Adults: A Summary of the Evidence for the U.S. Preventive Services Task Force. Ann Intern Med. ;140:128–141. doi: 10.7326/0003-4819-140-2-200401200-00015
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Published: Ann Intern Med. 2004;140(2):128-141.
Endocrine and Metabolism, Guidelines, Thyroid Disorders.
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