Will radioactive iodine treatment hurt my child in the long run?

Not likely: The primary long term effect of radioiodine treatment (for hyperthyroidism) is that the thyroid gland shuts down. Lifelong daily use of a throid hormone repacement will be necessary. As far as the radiation goes, the small amount is trapped in the gland and decays. There is no long term risk of thyroid cancer or leukemia in these patients. Pregnancy after treatment was not marked by anomalies.

No: Consider pretty safe.

Simple answer is no: Although long term data is lacking, the current guidelines recommend rai as first choice for treatment of hyperthyroidism/Grave's (in the US) if child's age is above 7yrs of age. Medication and surgery are other options and each choice has it's pros and cons. I personally tend to opt for pharmacologic treatment if presentation is mild.Talk with your endocrinologist.