Causes

Genes are composed of sequences of DNA molecules that control cell functions. Mutations of DNA are alterations that can be inherited or acquired as a result of damage during life. Thyroid cancer develops when mutations in a thyroid cell's genes fail to regulate cell growth and reproduction, leading to uncontrolled proliferation of cells, which form a malignant tumor.

DNA damage leading to thyroid cancer may result from exposure to environmental toxins, such as radiation. A history of radiation exposure is important to some cases of papillary and anaplastic cancer. Medullary cancer is closely linked to inherited mutations found in families with a history of thyroid cancer or other endocrine tumors. Mutations of DNA as part of aging are believed to contribute significantly to anaplastic thyroid cancer.

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This article was reviewed and updated June 2007.