A number of environmental, genetic, and gender- or age-related factors may increase your risk for developing thyroid cancer. Having a risk factor means that you have an increased chance of developing the disease, not that you will develop it. The following is a list of potential risk factors:
- Age between 20 and 55 years old. While thyroid cancer can occur at any age, approximately two out of three cases are diagnosed in people age 20 to 55.
- Female gender. Women are three times more likely to develop thyroid cancer than men.
- Exposure to radiation. From the 1920s to the 1950s, people were routinely treated with high doses of radiation for common head and neck ailments, such as acne and enlarged tonsils, because the risks were unknown. Also during the 1950s some people were exposed to radiation during atomic weapons testing. Others have been exposed because of accidents, such as happened at the nuclear power plant at Chernobyl in 1986 in the former Soviet Union.
- A history of goiter (enlarged thyroid) or colon polyps. Families with a history of goiter or colon polyps (growths in the colon) are at higher risk for thyroid cancer.
- A diet low in iodine. Follicular thyroid cancer is known to be more prevalent in countries where people have low iodine intake in their diet. In the United States, iodine is added artificially to salt and other foods to ensure we eat enough of it.
- Family history of thyroid disease or thyroid cancer.
- Certain genetic conditions such as Multiple Endocrine Neoplasia (MEN) increase the risk of thyroid cancer. Familial MTC occurs because of an abnormal gene that is passed from generation to generation. Most people with MEN, type II, will develop MTC.
- Race. Asian and white Americans are more likely to have thyroid cancer than blacks.
- Reproductive history. Women whose last pregnancy occurred at age 30 or later may have a higher risk of thyroid cancer.