Radioactive iodine is the way to go. I had a case of hyperactive thyroid causing the right node to enlarge. My endocrinologist wanted to do a low dose radioactive iodine, in an effort to cripple the thyroid and curb its over activity. This would almost assuredly have resulted in a hypo-active thyroid. I refused that and switched endos and had a surgeon remove the enlarged node. So far so good.

A word of caution. I know a gentleman whose thyroid was destroyed by radiation on a nearby tumor. One day, he forgot to take his medication and about halfway through the day, he was in a bad way. To quote him, he thought he was dying. After he took his meds it took the rest of the day to recover.