Commonly asked questions about thyroid function.

Thyroid function abnormalities in asymptomatic outpatients are common. When a patient is found to have an abnormality in thyrotropin (thyroid-stimulating hormone) or free or total thyroxine (T4), a review of the patient's medications and a careful neck examination will usually provide the explanation. Further diagnostic laboratory studies should include additional tests of T4 or thyrotropin. Determining the presence of antimicrosomal antibodies is useful for further assessment of "subclinical" hypothyroidism, and measures of protein binding (T4-binding capacity or T4-binding protein electrophoresis) help confirm a suspected congenital or acquired abnormality of T4 binding. Recognition of euthyroid hypothyroxinemia and hyperthyroxinemia is important in order to avoid intervention with inappropriate treatment. Management of subclinical hypothyroidism and hyperthyroidism necessitates clinical judgment about the patient's symptom profile and risks for long-standing or progressive thyroid dysfunction.