A 20-year-old woman complains of rapid enlargement of her thyroid gland over the last six months. There is no history of fever, weight loss, dysphagia, hoarseness, or ocular problems.

Her medical and surgical histories are unremarkable, although her family history is significant for medullary thyroid cancer diagnosed in her 48-year-old mother just 2 weeks ago.

She only drinks socially and has never smoked. A complete blood count and thyroid function tests are within normal parameters.