The decision to use radio iodine (I131) treatment after surgery is made based on the size of the cancer and the risk of a recurrence. The Multi-Disciplinary Thyroid Cancer Team uses International Guidelines to help make an individual decision for each patient.
Radioactive iodine treatment is painless; it involves taking a capsule by mouth. The iodine131 goes into the bloodstream and kills only thyroid cells. No other cells in the body are harmed because they cannot take up iodine.
Thyroid Stimulating Hormone (TSH) encourages thyroid cells to take up the I131. It is necessary to have a high TSH level to make the treatment successful. There are two ways to achieve this: to stop taking Levothyroxine a few weeks before the therapy or to take TSH as an injection on each of the two days before the I131 is taken. This second option avoids the need to stop thyroid hormone replacement.
You can download a booklet with more information here:
Radioiodine Therapy Information