The Laboratory Diagnosis of Thyroid Disease

Thyroid dysfunction is common in adults. The reported prevalence of hypothyroidism is 2% and up to 17% for subclinical hypothyroidism. The prevalence of hyperthyroidism is 0.2% and up to 6% for subclinical hyperthyroidism. Accordingly, the American Thyroid Association has recommended that adults be screened for thyroid dysfunction beginning at age 35 and then every five years after that (Ladenson et al., Arch Intern Med 160:1573–1575, 2000). An understanding of the laboratory diagnosis of thyroid disease is important to clinical practice.