NORMAL THYROID TISSUE – I-131 is given to destroy overactive thyroid tissue (see Hyperthyroidism brochure) or to shrink thyroid glands that are functioning normally but are causing problems because of their size (see Goiter brochure). Patients are asked to follow some radiation precautions after treatment in order to limit radiation exposure to others (see chart). I-131 may occasionally cause mild pain in the neck that can be treated with aspirin, ibuprofen or acetaminophen. The RAI treatment may take up to several months to have its effect. Frequently, the end result of RAI treatment of hyperthyroidism is hypothyroidism, which is treated by thyroid hormone replacement (see Hypothyroidism brochure).
THYROID CANCER – Large doses of I-131 are used to destroy thyroid cancer cells (see Thyroid Cancer brochure). This is performed after the remaining thyroid cells (including any cancer cells) are stimulated by raising TSH levels by either withdrawing the thyroid hormone pills or by treating with recombinant human TSH. Patients are asked to follow some radiation precautions after treatment in order to limit radiation exposure to others (see below). Depending on state regulations, patients may have to stay isolated in the hospital for about 24 hours to avoid exposing other people to radiation, especially if there are young children living in the same home.