Among patients with untreated subclinical hypothyroidism, there is no single level of serum TSH at which clinical action is always either indicated or contraindicated. As the serum TSH concentration increases above 10 mIU/L, however, the basis for initiating treatment is more compelling. Clinical context is particularly important. This opinion reflects clinical experience and judgment as well as the literature that suggests improvement in symptoms55 and possible lowering of LDL cholesterol.56 There are no studies that demonstrate decreased morbidity or mortality with treatment. The potential risks of therapy are limited to the development of subclinical hyperthyroidism, which may occur in 14% to 21% of individuals treated with levothyroxine.39,40