Radioactive iodine may be used as a treatment for certain thyroid disorders and thyroid cancer.
The thyroid gland needs iodine to produce thyroid hormones. The follicular cells of the thyroid have channels or pores to actively absorb iodine for making thyroid hormone. Radioactive iodine takes advantage of the fact that thyroid cells and thyroid cancer cells absorb iodine; therefore, it has been used to diagnose or treat various thyroid disorders.
Iodine is made into two radioactive isotopes — I-123 and I-131 — that are commonly used in patients with thyroid disease. A radioactive isotope (RAI) is a substance that gives off radiation. RAI is given by mouth, in pill or liquid form. RAI is then absorbed by the thyroid cells and can be used to diagnose or treat thyroid problems.
I-131 is commonly used to treat thyroid disorders, such as hyperthyroidism, through RAI ablation (medically destroying the thyroid gland without surgery). In addition, large doses of I-131 are used to destroy thyroid cancer cells, which are killed after absorbing the dose of radioactive iodine.