A nonpregnant adult presents with new onset dysphagia and a visibly enlarged midline neck mass. Their diet is low in iodine. Which evaluation is most appropriate to determine whether this represents an iodine-deficiency goiter versus another thyroid disorder?

• A. Measure serum TSH and free T4 and obtain a thyroid ultrasound; low thyroid hormone with diffuse enlargement and supportive dietary history suggests iodine-deficiency goiter, while other patterns suggest alternate etiologies.
• B. Recommend complete avoidance of all iodine-containing foods permanently, since goiter is worsened by any dietary iodine.
• C. Advise immediate high-dose iodine supplementation without testing, because any goiter must be due to deficiency and quick correction is mandatory.
• D. Order a dental x-ray because goiter always originates from hidden dental infections and is best evaluated by oral imaging.

Answer: (A)