Figure 47.2.—Diagnostic algorithm for a low TSH level.

Key: TSH = thyroid-stimulating hormone; T₄ = thyroxine; T₃ = triiodothyronine; RAIU = radioactive iodine uptake.

^* Glucocorticoids, dopamine agonists, and phenytoin.

^† If TSH is again normal, discontinue monitoring.

NOTE: The management of subclinical hyperthyroidism is controversial. If subclinical hyperthyroidism is diagnosed, the patient should be assessed for clinical findings consistent with thyrotoxicosis, such as atrial fibrillation, osteoporosis, and neuropsychiatric symptoms. If these findings are present, the clinician may wish to consider further evaluation as suggested for T₃ toxicosis. Otherwise, it is reasonable to recheck TSH, free T₄, and free T₃ and monitor clinically for manifestations of thyrotoxicosis every 6 months.