Thyroid Cancer Causes, Risk Factors and Prevention

When you hear the words thyroid cancer, it’s normal to wonder why it happens and if anything could have been done to prevent it. You want clear and trustworthy information, along with advice on what to do next.

At Banner MD Anderson Cancer Center, we believe knowledge helps you feel more in control. Learning how thyroid cancer starts and what might increase your chance of getting it can guide your decisions and take care of your health. 

How thyroid cancer develops

Thyroid cancer happens when cells in your thyroid gland start to grow in an abnormal and uncontrolled way. Normally, thyroid cells grow, work and replace themselves at a steady pace. But sometimes changes in the cells, called mutations, make them grow too fast or ignore signals that tell them to stop growing.

These changed cells can form a lump called a nodule. Most thyroid nodules are not cancerous, but some can turn cancerous. Cancer cells can spread to nearby lymph nodes, and in rare cases, to other parts of the body. 

There are several types of thyroid cancer and each starts in a different kind of thyroid cell. The most common and slowest growing type is papillary thyroid cancer. Other types include:

• Follicular thyroid cancer
• Medullary thyroid cancer
• Oncocytic thyroid cancer/Hürthle cell thyroid cancer (also called oxyphilic cell carcinoma)
• Poorly differentiated thyroid cancer (a rare form)
• Anaplastic thyroid cancer (a rare form that grows quickly)

Each type acts differently and has its own causes or risk patterns. 

Learn more about the different types of thyroid cancer.

Risk factors for thyroid cancer

A risk factor is anything that can increase your chance of developing a disease. Having one (or even several) risk factors doesn’t mean you will get thyroid cancer. Many people who are diagnosed have no known risks at all. Still, knowing your risks can help you make informed choices about your health. Common risk factors include:

1. Family history

Having a first-degree relative (parent, brother, sister or child) with thyroid cancer raises your risk. However, most people with thyroid cancer do not have a family history.

2. Radiation exposure 

Exposure to radiation, especially during childhood, can increase the risk of papillary thyroid cancer. This includes radiation therapy to the head, neck or chest for other health problems. People exposed to radiation from nuclear accidents or weapons also have a higher risk. 

3. Age and gender

Thyroid cancer can occur at any age, but it’s most often diagnosed in people ages 30 to 60. Women are about three times more likely than men to develop the disease. The reasons for this are not fully understood.

4. Low iodine intake

Iodine helps your thyroid make hormones. Not getting enough iodine may raise the risk for follicular thyroid cancer. This type of cancer is more common in parts of the world where people don’t get much iodine in their diets. In the U.S., this is less common because table salt contains added iodine.

5. Certain genetic conditions

Some hereditary (inherited) conditions can increase the risk of thyroid cancer, especially medullary thyroid cancer and some types of non-medullary thyroid cancers. Examples include:

• Multiple endocrine neoplasia type 2 (MEN2): Caused by mutations in the RET gene. It greatly increases the risk of medullary thyroid cancer and can affect other glands.
• Familial medullary thyroid cancer (MTC): A hereditary form of medullary thyroid cancer that occurs without the other features of MEN2.
• Cowden syndrome: Linked to PTEN gene mutations. It increases the risk of several cancers, especially follicular thyroid cancer.
• Familial adenomatous polyposis (FAP): Related to mutations in the APC gene. Best known for causing colon polyps, it also raises the risk of papillary thyroid cancer.   
• DICER1 syndrome: An inherited condition that increases the risk of multiple tumor types, including rare thyroid cancers. 
• Carney complex: A rare disorder that raises the risk of endocrine tumors and may be linked to thyroid nodules and cancers. 

These conditions are uncommon but if they run in your family genetic counseling and regular checkups can help with early detection.

6. Having another thyroid condition

A history of thyroid nodules or an enlarged thyroid gland can increase your risk, though most nodules are not cancerous. People with Hashimoto’s disease may also have a slightly higher risk of developing thyroid cancer.

7. High body weight

Some studies suggest that high body weight may be linked to a higher risk of thyroid cancer, although the exact reason is unclear. 

Should I consider genetic testing?

Genetic testing can help you understand your risk for certain types of thyroid cancer. It can’t predict when cancer will develop or how it will behave. But it can give you and your family helpful information and guide your care. 

You may want to talk to your provider about genetic testing if you have:

• A family history of MTC
• A known family history of MEN2
• A diagnosis of MTC at a young age
• A close family member who tested positive for an RET mutation

Learn more about genetic counseling at Banner MD Anderson. 

Can thyroid cancer be prevented? 

There is no guaranteed way to prevent thyroid cancer, since many risk factors are out of your control. Still, there are steps you can take to lower your risk and stay aware of changes in your body.

• Avoid unnecessary radiation: Medical imaging, such as CT scans, should be used only when needed. Today’s imaging uses much lower doses than in the past, but it’s still helpful to avoid unnecessary exposure. 
• Know your family history: If thyroid cancer runs in your family, talk to your health care provider about genetic counseling or testing. Understanding your risk early can help your care team watch for problems before they start.
• Support a healthy thyroid: A balanced diet with enough iodine helps your thyroid work properly. Many people get enough iodine through iodized salt, dairy, eggs and seafood. 
• Schedule routine health check-ups: See your health care provider regularly for wellness visits, including thyroid exams. 

Stay alert to symptoms

You may not be able to prevent thyroid cancer but catching it early can make a difference. Talk to your primary care provider or a thyroid specialist if you notice:

• A new lump or swelling in your neck
• Ongoing hoarseness or voice changes
• A cough that does not go away
• A cough with blood
• Trouble swallowing or breathing
• Pain in the neck or throat
• Enlarged lymph nodes in the neck
• A family history of thyroid cancer
• A history of childhood radiation exposure

Even if your symptoms seem mild, it’s always better to get them checked. Most thyroid nodules are not cancerous, but an exam can give you peace of mind or help you start treatment early if needed. 

Learn more

• Signs of thyroid cancer
• How thyroid cancer is diagnosed
• Treatment options and support services

Take the next step

Banner MD Anderson is a leader in thyroid cancer treatment, patient care and research. Our patients have access to:

• A multidisciplinary team of experts, including surgeons, endocrinologists, oncologists, nurses and support staff
• Advanced imaging and screening tools
• Comprehensive treatment options
• Genetic counseling and testing
• Ongoing care and support

Our goal is simple: To help you understand your diagnosis, feel good about your choices and get the best care for thyroid cancer. 

When you’re ready, our team is here to help you move forward. 

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