Thyroid disorders are common in elderly patients. In fact, the most common form of thyroid dysfunction in the elderly is subclinical hypothyroidism. Subclinical hypothyroidism is a biochemical state characterized by an increased serum thyroid-stimulating hormone and normal levels of serum-free T4 and free T3. Much attention has been focused on this clinical entity recently, but it remains controversial whether early thyroid replacement therapy improves outcomes in elderly patients with asymptomatic subclinical hypothyroidism. There is a dearth of critical evidence on the effects of subclinical hypothyroidism on target tissues, the natural history of early thyroid dysfunction, and the net benefits and harms of long-term treatment with thyroid hormones. This article reviews the available information on the aging thyroid gland, subclinical hypothyroidism, and issues concerning treatment in asymptomatic elderly patients.