What are the risk factors for thyroid cancer?
While the exact cause of most thyroid cancers is not known, several risk factors have been linked to the disease. A risk factor is anything that affects a person's chance of getting a disease such as cancer. Different cancers have different risk factors. For instance, smoking is a risk factor for cancers of the lung, mouth, larynx (voice box), bladder, kidney, and several other organs.
But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you will get the disease. And many people who get the disease may not have had any known risk factors. Even if a person with thyroid cancer has a risk factor, it is very hard to know what part that risk factor may have played in the cancer.
Below are some risk factors that make a person more likely to develop thyroid cancer.
Gender and age
Thyroid cancers (like almost all diseases of the thyroid) happen about 3 times more often in women than in men. The reason for this is not known.
Thyroid cancer can occur at any age. But women are most likely to get it in their 40s or 50s, while men are more likely to get it in their 60s or 70s
A diet low in iodine
Follicular thyroid cancers are more common in places where people's diets are low in iodine. In the United States, most people get enough iodine in their diet because it is added to table salt and other foods.
Exposure to radiation is a proven risk factor for thyroid cancer. Sources of such radiation include certain medical treatments and radiation fallout from power plant accidents or nuclear weapons.
Having had head or neck radiation treatments in childhood is a risk factor for thyroid cancer. Risk depends on how much radiation is given and the age of the child. Before the 1960s, children were sometimes treated with low doses of radiation for things we wouldn't use radiation for now, like acne, ringworm, and other problems. Years later, the people who had these treatments were found to have a higher risk of thyroid cancer. Being exposed to radiation as an adult carries much less risk of thyroid cancer.
Hereditary conditions and family history
Several inherited conditions have been linked to different types of thyroid cancer.
Medullary thyroid cancer Some types of a fairly rare type of thyroid cancer (familial medullary thyroid carcinomas or FMTC) result from inheriting an abnormal gene. FMTC can occur alone, or it can be seen along with other tumors, as part of a syndrome called multiple endocrine neoplasia type 2 (MEN 2).
Other thyroid cancersPeople with certain inherited medical problems are at higher risk for more common forms of thyroid cancer. Higher rates of the disease occur among people with rare genetic conditions such as familial adenomatous polyposis (FAP), Gardner syndrome, Cowden disease, and Carney complex, type I. To learn more about these conditions, please see our document, Thyroid Cancer.
Papillary and follicular thyroid cancers also seem to run in some families without known genetic conditions. Having a parent, brother, sister, or child with thyroid cancer increases your risk of thyroid cancer.
If you think you might be at increased risk of thyroid cancer, talk to your doctor. He or she might suggest genetic counseling if your background warrants it.
*Information from the American Cancer Society