Subclinical thyroid disease.

Subclinical thyroid disease, a term applied to patients with no or minimal thyroid-related symptoms with abnormal laboratory values, is diagnosed more frequently with the use of thyroid-stimulating hormone (TSH) screening and newer high-sensitivity assays. These are laboratory diagnoses, with subclinical hypothyroidism defined as an elevated TSH with a normal free thyroxine and triiodothyronine concentration, and subclinical hyperthyroidism as a subnormal TSH with normal free thyroxine and triiodothyronine levels. Although studies defining which patients require treatment are few, decisions should be individualized based upon laboratory values and symptoms. This article reviews the etiologies, diagnoses, treatments and indications, and monitoring of patients with subclinical thyroid disease.