If you are hyperthyroid and have an enlarged thyroid, then I can tell you what worked for me.
After going to 2 doctors who suggested ablating my thyroid (rendering it functionless for the rest of my life) with radioactive iodine, I consulted with a 3rd doctor. He said to avoid all Iodine or kelp, both in food (seaweed, fish & fish oil) and via supplements. After 1 year, my thyroid is now normal in size/function and my other related hyperthyroid symptoms have completely disappeared.
Too much kelp or Iodine makes the thyroid overproduce hormones, become enlarged and produce nodules. I wish I had known this years earlier because my poor Mom is battling thyroid cancer. Her enlarged thyroid is growing inward and is choking her. Her windpipe is gettting smaller and smaller.