The thyroid is a small gland located at the front of the neck, just at the spot where a bow tie would rest. It has left and right halves (called lobes) that look like a butterfly’s wings. It manufactures the hormones that help control metabolism and growth. To do its job, it needs a chemical element called iodine that the body absorbs from the foods you eat and the water you drink and concentrates it in the thyroid gland to produce these hormones.

Thyroid treatment with radioactive iodine has been used successfully for over 40 years to treat two main conditions:

  1. hyperthyroidism (overactive thyroid)
  2. thyroid cancer

Since the thyroid rapidly absorbs any iodine we ingest, a low iodine diet is maintained prior to treatment (thus depleting the Thyroid gland).  Once it is depleted of iodine, then, radioactive iodine (I131) is given by pill or liquid. The radioactive version (I131) is quicky absorbed.  Chemically, radioactive iodine acts in the same way as non-radioactive iodine.

The beta particles, one type of radiation emitted by the I131 as it decays, bombard the thyroid cells and destroy them.  The real advantage of this treatment is that the beta particles can only travel a few millimeters in tissue, so the cell damage is limited to the immediate thyroid tissue.  Also, since this is almost the only tissue which uses iodine, other organs and tissues are not negatively effected. You may have heard this treatment described as a “magic bullet”.

With hyperthyroid treatment, the goal is to destroy all or part of the overactive thyroid gland. Hormone replacement pills may need to be taken afterward.

In the case of thyroid cancer treatment, there is a difference.  Typically the thyroid is first removed surgically.  Radioactive iodine is administered in a larger dose than for hyperthyroidism.  Any tissue that was not removed, as well as any related tumors which may have metastasized away from the Thyroid gland, will take up the radioactive iodine and that tissue will be destroyed. Hormone replacement pills will need to be taken afterward.

These radioactive iodine treatments have proven to be safe and highly effective.