Cat (feline) Dog (canine) Hyperthyroidism I-123 I-124 I-125 Q and A Radioiodine (I-131) Thyroid The Many Isotopes of Radioiodine and Their Uses in Medicine My question is about using radioactive iodine (radioiodine) to treat hyperthyroidism. Is radioiodine-131 (131-I) the only radioi… Thursday, August 8, 2013 Add Comment Edit