It is not clear what causes thyroid cancer. Thyroid cancer occurs when the cells in your thyroid undergo genetic changes (mutations). The mutations allow the cells to grow and multiply rapidly. Unlike normal cells, they also lose the ability to die. The accumulating abnormal thyroid cells form a tumour. The abnormal cells can invade nearby tissue and spread throughout the body.
Risk factors
Factors that may increase the risk of thyroid cancer include:
- Female sex: Thyroid cancer is more common in women than in men.
- Exposure to high levels of radiation: Examples of exposure to high levels of radiation include radiation treatments for head and neck cancer, and fallout from sources such as nuclear power plant accidents and nuclear weapons testing.
- Certain inherited genetic syndromes: The genetic syndromes that increase the risk of thyroid cancer are familial medullary thyroid cancer and multiple endocrine neoplasia.