Clinical characteristics: Suppressed TSH Normal thyroid hormone levels Hyperthyroid symptoms may or may not be present Etiology: Exogenous thyroid hormone Graves disease Nodular thyroid disease Indications for treatment: TSH persistently less than 0.1 µU/mL OR TSH 0.1-0.5 µU/mL plus additional risk factors: Age over 65 Heart disease Osteoporosis Nodular thyroid disease