What Causes Thyroid Cancer | UCLA Endocrine Center

Hi, I am James Wu, an Endocrine Surgeon at the UCLA Health Endocrine Center. Today, I want to talk to you about what causes papillary thyroid cancer, the most common type of thyroid cancer.

There are many things that we know and many things that we don't know about why people get thyroid cancer. Let me begin with the things that we know for sure.

One significant risk factor for thyroid cancer is radiation exposure, which can occur through various means such as being near accidents like Chernobyl or Fukushima, or undergoing radiation treatments to the head and neck for other types of cancers (most often lymphoma in childhood). The thyroid gland is most vulnerable to radiation before the age of 15, after which it takes an average of 5 years for thyroid cancer to subsequently develop. It is important to note that small amounts of radiation from routine procedures like X-rays or CT scans, as well as living in proximity to a nuclear power station, are not associated with an increased risk of developing thyroid cancer.

Some families carry genetic (germline) mutations that put them at higher risk of thyroid cancer, which is why we will always ask if anyone else in the family has thyroid problems or thyroid cancer. However, only about five percent or so of Papillary Thyroid Cancers are caused by inherited syndromes. Most cancers develop sporadically, meaning that the arise because of chance. The vast majority of our patients have never been exposed to radiation and don't have a strong family history of papillary thyroid cancer. Despite these factors, some individuals still wonder why they develop thyroid cancer, prompting further exploration into potential causative factors.

So why do people get thyroid cancer?

Well, there's a short answer, and there's a long answer. The short answer is, unfortunately, just bad luck. The longer answer is this: our thyroid glands are made up of many, many cells. Just like we need to constantly grow new hair and skin to replace dead, aging, and damaged cells, we need to grow new thyroid cells to replace the old ones. Each time a thyroid cell divides into new cells, it has to copy all the DNA over to the new cell. Each cell contains millions of pieces of DNA, and each time you try to copy all that DNA, some mistakes will be made. When mistakes happen in just the wrong place, the cell can become abnormal by reproducing (making copies of) itself in an uncontrolled way. Cancer is a disease of abnormal cell growth and invasion. Uncontrolled cell growth, combined with the spreading of cells into adjacent neighboring organs (invasion) or distant organs (metastasis) is what defines cancer.

Several studies have investigated various factors that might elevate the risk of thyroid cancer. These factors encompass smoking, obesity, and exposure to environmental toxins. Presently, the existing scientific data do not conclusively establish a clear correlation between these factors and the development of thyroid cancer.

No matter what the cause may be, the good news is that most thyroid cancers respond well to treatment. Most people who are diagnosed with thyroid cancer go on to live long, full lives after receiving appropriate medical care. To learn more about thyroid cancer treatment, we invite you to explore additional resources available on our website. If you are considering a consultation, you can conveniently submit an appointment request online or reach out to our office via phone.

Key Insights:

  • Radiation exposure – by this we mean significant exposure as would occur with nuclear fallout or cancer treatment – is a risk factor for subsequent thyroid cancer development, particularly if the exposure occurred before age 15.
  • Germline mutations (those that can be passed from parent to child) increase the risk of thyroid cancer, but these account for only a small percentage of cases.
  • Most cases of papillary thyroid cancer occur without any identified cause, suggesting it is largely a matter of chance or bad luck.
  • Each time thyroid cells divide and copy DNA, mistakes can occur, leading to abnormal cells and potentially cancer.
  • While smoking, obesity, and pesticide exposure have been studied as potential risk factors, their direct relationship with thyroid cancer is still uncertain.
  • Papillary thyroid cancer (the most common type of thyroid cancer) has favorable treatment outcomes, and the long-term prognosis is generally excellent.

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