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What Causes Thyroid Cancer?

written by: Emma Lloyd • edited by: Leigh A. Zaykoski • updated: 6/15/2010

What is thyroid cancer? Who gets this type of cancer? What causes thyroid cancer? Find out the answers to these questions in the following article.

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    About Thyroid Cancer

    The thyroid is a small endocrine gland located at the front of the neck. This gland produces several hormones, which are involved in regulating body metabolism and temperature. In most cases, thyroid cancer develops in thyroid cells that are involved in the production of these hormones.

    There are several types of thyroid cancer, each of which varies in frequency and severity. The most common types are called follicular adenocarcinoma and papillary adenocarcinoma of the thyroid.

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    What causes Thyroid Cancer?

    Some cancers have only one "cause", in that they develop spontaneously in the body without the involvement of any known predisposing factors. This is not the case with thyroid cancer. What causes thyroid cancer?

    There are several possible thyroid cancer causes and risk factors, as this cancer can develop as a result of either natural or artificial stimuli. Some thyroid cancer risk factors can be minimized, while others can not.

    For example, age, sex, and family history are all risk factors for thyroid cancer, but the influence of these risk factors cannot be altered.

    • Age: Most people who are diagnosed with this type of cancer are over the age of forty.
    • Sex: Thyroid cancer is much more common in women than in men, by a ratio of three to one. The reason for this difference is not well understood. One possible explanation is that the difference is related to hormones such as estrogen and progesterone, which are present in both sexes, but are present in much higher quantities in women.
    • Family history: Some thyroid cancers can “run in the family”. This is because there are certain inheritable genetic mutations that can increase the risk of thyroid cancer. Mutations in genes called RET, PTEN, and APC are known to increase this risk.

    Other thyroid risk factors and causes can be alleviated or prevented. These include iodine deficiency and radiation exposure.

    • Iodine deficiency: This is a risk factor for some types of thyroid cancer, because iodine is essential for normal thyroid function. The relationship between iodine deficiency and thyroid cancer is not clear. The main evidence for iodine deficiency as a risk factor comes from studies in which countries where iodine deficiency is common have higher rates of thyroid cancer in the population.

    • Radiation exposure: Exposure to radiation is one of the strongest thyroid cancer risk factors. The risk is even higher if the exposure occurred in childhood. In Western countries the most common way for this exposure to have occurred is in medical treatments such as that for overactive thyroid. Radiation therapy was also used in the mid-twentieth century to treat enlargement of neck tissues such as the thymus and adenoids.

    Most people in Western countries are not at risk of iodine deficiency. In countries where iodine deficiency is common, the only way to prevent the slightly higher risk of thyroid cancer is to ensure adequate and consistent iodine intake.

    Some people who receive radiotherapy treatment for hyperthyroidism can reduce their future thyroid cancer risk with the use of potassium iodide tablets. (These should only be used with the advice and supervision of a doctor.)

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    References

    American Cancer Society: What is Thyroid Cancer

    Memorial Sloan-Kettering Cancer Center: Risk Factors

    Memorial Sloan-Kettering Cancer Center: Thyroid Cancer Overview

    National Institute of Health MedlinePlus: Thyroid Cancer