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Risk Factors and Symptoms of Thyroid Cancer

Risk Factors

A risk factor is anything that affects a person’s chance of getting a disease such as cancer. Different cancers have different risk factors.

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 have few or no known risk factors. Even if a person with thyroid cancer has a risk factor, it is very hard to know how much that risk factor may have contributed to the cancer. There is no known prevention. Awareness of risk (such as previous radiation therapy to the neck) can allow earlier diagnosis and treatment.

  • Gender and age
    It's unclear why, but thyroid cancers (like almost all diseases of the thyroid) occur about 3 times more often in women than in men.
    Thyroid cancer can occur at any age, but the risk peaks earlier for women (who are most often in their 40s or 50s when diagnosed) than for men (who are usually in their 60s or 70s).
  • A diet low in iodine
    Follicular thyroid cancers are more common in areas of the world 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. A diet low in iodine may also increase the risk of papillary cancer if the person also is exposed to radioactivity.
  • Radiation
    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. In general, the risk increases with larger doses and with younger age at treatment.
  • Hereditary conditions and family history
    Several inherited conditions have been linked to different types of thyroid cancer, as has family history. Still, most people who develop thyroid cancer do not have an inherited condition or a family history of the disease:
    • Medullary thyroid cancer:
      About 1 out of 3 medullary thyroid carcinomas (MTCs) result from inheriting an abnormal gene. These cases are known as familial medullary thyroid carcinoma (FMTC).
    • Other thyroid cancers
      People with certain inherited medical conditions have a higher risk of more common forms of thyroid cancer. Higher rates of thyroid cancer occur among people with uncommon genetic conditions such as:
      • Familial adenomatous polyposis (FAP):
        People with this syndrome develop many colon polyps and have a very high risk of colon cancer. They also have an increased risk of some other cancers, including papillary thyroid cancer.
      • Cowden disease:
        People with this syndrome have an increased risk of thyroid, endometrial (uterine), and breast cancers. The thyroid cancers tend to be either the papillary or follicular type.
      • Carney complex, type I:
        People with this syndrome may develop a number of benign tumors and hormone problems. They also have an increased risk of papillary and follicular thyroid cancers.

    Signs and Symptoms of Thyroid Cancer

    Thyroid cancer most often begins as a lump or nodule on or in the thyroid gland. In general, the symptoms will relate to the presence of this lump or nodule:

    • A lump in the neck, sometimes growing quickly
    • Swelling in the neck
    • Pain in the front of the neck, sometimes going up to the ears
    • Hoarseness or other voice changes that do not go away
    • Trouble swallowing
    • Trouble breathing
    • A constant cough that is not due to a cold

    It's important to note that nearly all thyroid cancers have little to no symptoms; and lab tests for thyroid cancer often come back negative (even when there is cancer). The best screening method -- and the best course of action should you display any of the above symptoms -- is to have your doctor check your neck on a regular basis.

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Learn more about thyroid and other endocrine diseases

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