Abnormal thyroid function tests are common for older adults, but the clinical significance of abnormal results and the need for treatment vary. Nonthyroidal illness (eg, low T3 and T4 syndromes) needs to be ruled out before making the diagnosis of hypothyroidism. Overt hypothyroidism and myxedema coma always require treatment, but treatment of subclinical hypothyroidism is not as clear. The purpose of this review article is to summarize existing data in the elderly population on the etiology, diagnosis, and management of overt hypothyroidism and subclinical hypothyroidism.