This decision is complicated by the fact that many hyperfunctional thyroid glands are not physically enlarged, thus many hyperfunctional, normally sized glands will not be removed, and the cat will still be hyperthyroid, requiring a second surgery. Also, if all thyroid tissue is removed, the owner is back to giving at least one pill per day for the remainder of the cat's life, this time thyroid supplementation. Obviously, this tissue would be missed from a ventral incision in the neck. The third option for the treatment of hyperthyroidism is the administration of radioactive iodine. The advantages of radioiodine cure are many.
Recurrence rate is extremely low.
The return to a euthyroid state is rapid, as circulating thyroid hormone levels drop precipitously within 48 hours post-administration, and there are essentially no side effects. Normal thyroid cells are suppressed through negative feedback loops, and as such do not concentrate any of the iodine. In this way, cats treated with radioactive iodine typically do not need any medication and are euthyroid. The only disadvantage to the use of radioiodine is that the cat must be hospitalized in a special facility for about 4-5 days, while the animal is excreting the radioactivity. The typical hyperthyroid cat treated with radioactive iodine will gain significant weight during the short hospitalization period, have a good appetite and do well.