Treatment of medullary carcinoma of the thyroid with I-131

We present a patient with radioiodine concentration in pulmonary metastases presumably arising from medullary carcinoma of the thyroid. Transient symptomatic improvement occurred after treatment with a large dose of sodium iodide (I-131). Although radioiodine concentration in medullary carcinoma of the thyroid is rare, the findings in this patient and in other recent reports suggest that an attempt should be made to determine whether a medullary carcinoma concentrates radioiodine. If so, I-131 treatment might be beneficial.