Radioactive iodine is sometimes given to people with overactive thyroid glands or thyroid cancer to destroy part of the gland or mop up any remaining tumor cells after surgery. For days after the isotope injection, patients are so radioactive that they are advised not to kiss anyone or to sleep close to anyone (including their pets), and to maximize the distance between themselves and children or pregnant women.74 The treatment can be very effective, but all that radiation exposure appears to increase the risk of developing new cancers later on.
