Thyroid Cancer Risk Iodine

Maintaining appropriate levels of iodine for thyroid function is one of the human body’s important balancing acts. Your thyroid needs iodine in order to produce thyroid hormones, so problems develop if you don’t get enough iodine. When your iodine level is insufficient for proper thyroid functioning, goiters (enlarged thyroid glands) or hypothyroidism (an underactive thyroid) can result.

Insufficient iodine intake is particularly dangerous for pregnant women because it increases the risk of birth defects. Children with iodine deficiencies may have delayed mental development.

However, too much iodine can either block the release of thyroid hormones, or it can result in over-production of thyroid hormones. The latter can occur when an individual switches from low iodine to high iodine intake.

The thyroid is the only gland that absorbs iodine, a characteristic that comes into play in the treatment of hyperthyroidism and thyroid cancer. In patients with an overactive thyroid, radioactive iodine is used to eliminate non-cancerous nodules that produce excessive levels of thyroid hormones.

After surgery for cancer of the thyroid, radioactive iodine is often used as a follow-up treatment to destroy any remaining thyroid cancer cells.

Where You Get Iodine and How Much You Need

Iodine is the raw material from which the thyroid manufactures thyroid hormones tri-iodothyronine (T3) and thyroxine (T4).

Your body can’t manufacture iodine alone, so you have to obtain it through your diet, and that’s not always easy. While foods like dairy products and seafood can be good sources of iodine, medical historians credit the introduction of iodized salt in the 1920s as the key to reducing iodine deficiencies in the U.S. Still, experts at Harvard Medical School estimate that 7 to 8 percent of Americans have a moderate iodine deficiency. This is a slight increase over rates from the 1970s. Internationally, an estimated 40 percent of the world’s population is at risk for iodine deficiency.

The recommended daily amount of iodine is about 200 micrograms a day for pregnant women, 90 to 120 micrograms for children and 150 micrograms for adults.

Radioactive Iodine and Thyroid Treatment

Radioactive iodine is often used to treat thyroid problems, particularly hyperthyroidism and papillary and follicular thyroid cancers. Because it actually destroys thyroid tissue, the use of radioactive iodine has been shown to be quite effective.

When used to treat an overactive thyroid, radioactive iodine has a success rate between 75 and 100 percent, although patients commonly have to take replacement thyroid hormones. When used after surgery for cancer of the thyroid, radioactive iodine can help clear the body of any remaining cancer cells.

Some physicians prescribe a low-iodine diet before treating patients with radioactive iodine.

If you have concerns about iodine in your diet, and the relationship between the thyroid and iodine, be sure to discuss them with your physician.


American Thyroid Association staff. (2010). Iodine deficiency. Retrieved March 10, 2010, from the American Thyroid Association Web site:

Drucker, D. (2010). Iodine. Retrieved March 14, 2010, from the MyThyroid Web site:

Mathur, R. (2006). Thyroid