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in the clinic

Hypothyroidism
Screening Diagnosis Treatment Practice Improvement CME Questions
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Section Editor Christine Laine, MD, MPH Sankey Williams, MD Barbara Turner, MD Physician Writer Michael T. McDermott MD

The content of In the Clinic is drawn from the clinical information and education resources of the AmericanCollege of Physicians (ACP), including PIER (Physicians’ Information and Education Resource) and MKSAP (Medical Knowledge and Self-Assessment Program). Annals of Internal Medicine editors develop In the Clinic from these primary sources in collaboration with the ACP’s Medical Education and Publishing Division and with the assistance of science writers and physician writers. Editorial consultants fromPIER and MKSAP provide expert review of the content. Readers who are interested in these primary resources for more detail can consult http://pier.acponline.org and other resources referenced in each issue of In the Clinic. CME Objective: To provide information on the screening, diagnosis, and treatment of hypothyroidism. The information contained herein should never be used as a substitute forclinical judgment. © 2009 American College of Physicians

in the clinic

1. Tunbridge WM, Evered DC, Hall R, et al. The spectrum of thyroid disease in a community: the Whickham survey. Clin Endocrinol (Oxf ). 1977;7:481-93. [PMID: 598014] 2. Canaris GJ, Manowitz NR, Mayor G, et al. The Colorado thyroid disease prevalence study. Arch Intern Med. 2000;160:52634. [PMID: 10695693] 3. Hollowell JG,Staehling NW, Flanders WD, et al. Serum TSH, T4, and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab. 2002;87:48999. [PMID: 11836274] 4. Danese MD, Powe NR, Sawin CT, et al. Screening for mild thyroid failure at the periodic health examination: a decision and cost-effectiveness analysis. JAMA.1996;276:285-92. [PMID: 8656540] 5. Singer PA, Cooper DS, Levy EG, et al. Treatment guidelines for patients with hyperthyroidism and hypothyroidism. Standards of Care Committee, American Thyroid Association. JAMA. 1995;273:808-12. [PMID: 7532241] 6. Screening for thyroid disease: recommendation statement. Ann Intern Med. 2004;140:125-7. [PMID: 14734336] 7. Helfand M. Screening for subclinicalthyroid dysfunction in nonpregnant adults: a summary of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med. 2004;140:128-41. [PMID: 14734337] [Full Text] 8. Surks MI, Ortiz E, Daniels GH, et al. Subclinical thyroid disease: scientific review and guidelines for diagnosis and management. JAMA. 2004;291:228-38. [PMID: 14722150]

ypothyroidism is a condition in which the thyroidgland cannot make enough thyroid hormone to meet the requirements of peripheral tissues. It is the most common functional disorder of the thyroid gland. Primary hypothyroidism occurs when thyroid failure results from disease of the thyroid gland itself and it accounts for more than 99% of all cases of hypothyroidism (Figure 1). The most common causes of primary hypothyroidism in adults are chroniclymphocytic thyroiditis (Hashimoto disease); radioiodine thyroid ablation; thyroidectomy; high-dose head and neck radiation therapy; and medications, such as lithium, α-interferon, and amiodarone. Central hypothyroidism occurs when thyroid failure results from pituitary or hypothalamic disorders that cause insufficient production of thyroid-stimulating hormone (TSH) by the pituitary gland (Figure2). The most common causes of central hypothyroidism in adults are tumors, inflammatory conditions, infiltrative diseases, infections, pituitary surgery, pituitary radiation therapy, and head trauma.

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Primary hypothyroidism is overt when the serum TSH level is high and the serum total thyroxine (T4) or free T4 level is less than the population reference range. Subclinical hypothyroidism...