Evaluation and treatment of thyroid nodules: a clinical guide.

Thyroid nodules are inexplicably frequent and affect approximately one-third of the adult population. The appropriate clinical management is focused primarily on excluding thyroid cancer and also on evaluating thyroid dysfunction and mechanical obstruction. There remains no evidence that a benign thyroid nodule, once diagnosed appropriately, will progress to a malignant lesion. The initial evaluation should include a complete clinical review, a thyroid sonogram by an experienced sonographer, a laboratory assessment of thyroid function, and, where indicated, a cytological assessment of the nodule(s) by fine needle aspiration under ultrasound guidance. Only patients with suppressed serum thyroid-stimulating hormone levels, indicating hyperthyroidism, may need further evaluation by radioactive iodine uptake and scanning. Optimal treatment depends on the patient as well as the nodule characteristics. The usual options remain a simple annual follow-up to detect changes in nodule size and thyroid function and surgical removal. Levothyroxine therapy is now seldom indicated because of poor efficacy in nodule suppression and its inability to differentiate benign lesions from thyroid carcinoma. Clinical guidelines have a very arbitrary recommendation of aspiration biopsy in all lesions greater than 1 cm in size, but this proposal has no scientific basis and should always be viewed in the clinical context.