Which medication must be monitored with regular thyroid function tests?

Levothyroxine is a synthetic form of the thyroid hormone thyroxine (T4) and is predominantly used to treat hypothyroidism. Since the medication directly affects thyroid hormone levels in the body, it is essential to monitor thyroid function tests regularly to ensure that the dosage is appropriate and maintains thyroid levels within the normal range. Regular monitoring helps identify whether a patient is receiving too little or too much of the medication, preventing potential complications such as symptoms of hypothyroidism or hyperthyroidism.

Other medications listed, such as amlodipine, simvastatin, and metformin, do not primarily involve thyroid hormone regulation. Amlodipine is a calcium channel blocker for managing hypertension and angina, simvastatin is a statin for lowering cholesterol levels, and metformin is an oral hypoglycemic agent for managing type 2 diabetes. Therefore, they do not require the same level of thyroid function monitoring as levothyroxine does.