A risk factor is anything that increases a person's chance of getting a disease. Different diseases have different risk factors. Some risk factors can be controlled with lifestyle changes. Other risk factors cannot be changed.
For most patients, the specific reason why they develop thyroid cancer is not known. It is important to note that some patients with multiple risk factors never develop thyroid cancer. In fact, most people who have thyroid cancer have no obvious known risk factor.
Known risk factors for follicular and Hurthle cell thyroid cancer include:
Radiation exposure: Follicular and Hurthle Cell thyroid cancers are more common in people who have a history of exposure to significant ionizing radiation. Radiation-induced thyroid cancer can happen at any time between a few years after exposure to as long as 30 to 50 years later. Radiation exposure is broken down into three major categories:
- Childhood exposure: X-ray treatments were widely used in the 1940s and 1950s. This radiation was used to treat acne, enlarged tonsils, lymphomas, ringworm, enlarged thymus glands, and other ailments. X-rays were also used to measure foot sizes in shoe stores, and many people fondly remember seeing their "glowing green feet" and playing in those shoe fluoroscopes for hours while siblings were fitted for shoes. Children, younger than 15 years old, are most sensitive to radioactive damage to their thyroids.
- Medical Therapy: Radiation therapy to the head, neck, and upper chest are an increasingly common cause of radiation-induced thyroid cancer. Lymphoma, head and neck cancers, lung cancer, and breast cancer are some of the more common cancers that are associated with radiation exposure to the thyroid.
- Environmental exposure: Thyroid cancer can be caused by radioactivity released from nuclear incidents such as the 1986 nuclear accident at the Chernobyl power plant in Russia. Many of the children in areas of Russia and the Eastern Bloc countries were inadvertently exposed to radiation and went on to develop thyroid cancer. Some people may also be exposed to radiation at work. However, routine X-ray exposure (for example dental X-rays, chest X-rays, mammograms) have NOT been shown to cause thyroid cancer.
Iodine deficiency: Severe and prolonged iodine deficiency tends to increase the risk of developing follicular cancer. Iodine deficiency is not common in the United States or most of Europe.
Having one or more of the above risk factors does not mean that you will develop follicular or Hurthle cell cancer. Understanding your risk factors will help you determine, what, if any, precautions and whether there is any special screening you should consider.