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Thyroid Cancer Risk Factors


Updated: September 10, 2007

Thyroid Cancer Risk Factors

Certain factors increase your risk of developing thyroid cancer.

While it's important to learn how thyroid cancer develops, keep in mind that having one or more thyroid cancer risk factors does not mean that you will definitely develop the disease. Similarly, even if you have no risk factors, you can still develop thyroid cancer. But experts have found having one or more of the following risk factors does make it more likely that you will develop thyroid cancer. Here are the most important ones.

Too Little Iodine in the Diet

Iodine, a nutrient, is necessary for the thyroid to produce thyroid hormone. In areas where the diets do not include sufficient iodine, or foods like salt are not iodized, follicular thyroid cancer is more prevalent. Almost all salt in the U.S. has been iodized.

Exposure to Radiation

Exposure to radiation in neck area as a medical treatment -- especially as a child or young adult -- is a risk factor for thyroid cancer. In years past, radiation and x-rays were used to treat a wide variety of conditions, such as acne, scalp fungus, an enlarged thymus gland, enlarged tonsils or adenoids and Hodgkin disease. Also, exposure to radioactive fallout -- due to nuclear accidents (i.e., the Chernobyl explosion) and weapons testing (i.e., the western U.S. in the 1950s) -- is a risk factor for thyroid cancer in both children and adults.

Heredity/Genetics/Family History

An estimated 20% of patients with medullary thyroid cancer (MTC) develop the condition due to an abnormal gene. This gene can be passed on to offspring. Thyroid cancer that develops due to this genetic abnormality is called familial medullary thyroid carcinoma (FMTC). Family members who share this gene abnormality are at a greatly increased risk of medullary thyroid cancer.

There appears to be some hereditary basis for papillary thyroid cancer in some families, but the genetic basis has not been established yet.


Thyroid cancer affects women more than men, and in the United States, women are two to three times more likely than men to develop thyroid cancer.


Nearly two-thirds of those diagnosed with thyroid cancer are between the ages of 20 and 55.

Anaplastic thyroid cancer is most common in people over the age of 65.

More Information on Thyroid Cancer

Find out more about the symptoms of thyroid cancer and the procedures and tests used to diagnose thyroid cancer.


Braverman, MD, Lewis E., and Robert D. Utiger, MD. Werner and Ingbar's The Thyroid: A Fundamental and Clinical Text. 9th ed., Philadelphia: Lippincott Williams & Wilkins (LWW), 2005.

National Cancer Institute -- Thyroid Cancer Page

What You Need to Know About Thyroid Cancer, National Cancer Institute

American Cancer Society: Thyroid Cancer Guide

American Cancer Society: Thyroid Cancer Statistics

Thyroid Cancer Survivors Association (ThyCa)

Mary Shomon, About.com's Thyroid Guide since 1997, is a nationally-known patient advocate and best-selling author of 10 books on health, including "The Thyroid Hormone Breakthrough: Overcoming Sexual and Hormonal Problems at Every Age," "The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss," "Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You...That You Need to Know," "Living Well With Graves' Disease and Hyperthyroidism," "Living Well With Autoimmune Disease," "Living Well With Chronic Fatigue Syndrome and Fibromyalgia," and the "Thyroid Guide to Hair Loss." Click here for more information on Mary Shomon.

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