Which patient would be least suitable for radioactive iodine therapy?

• A. Pregnant woman with Hashimoto's thyroiditis
• B. 30-year-old patient with toxic adenoma
• C. 50-year-old patient with subacute thyroiditis
• D. Over age 65 Graves' disease

Answer: (A)

Radioactive iodine therapy works by delivering radiation to thyroid tissue to destroy overactive cells. A pregnancy is an absolute contraindication because the fetus is sensitive to thyroid radiation, which can cause fetal hypothyroidism and developmental problems. So a pregnant patient, even with Hashimoto’s, is least suitable for this treatment. By contrast, a toxic adenoma typically benefits from RAI since the overactive nodule takes up iodine while the rest of the gland is normal. Subacute thyroiditis isn’t treated with RAI because the thyrotoxic state comes from inflammatory release of stored hormone, not from increased iodine uptake. Graves’ disease, especially in an older patient, is a common indication for RAI as a definitive therapy.