A risk factor is any factor that is associated with increasing someone’s chance of developing a certain condition, such as cancer. Some risk factors are modifiable, such as lifestyle or environmental risk factors. Others cannot be modified, such as inherited factors or whether someone in the family has had cancer. 

Having one or more risk factors does not mean you will develop cancer. Many people have at least one risk factor but will never develop cancer, while others with cancer may have had no known risk factors. Even if a person with cancer has a risk factor, it is usually hard to know how much that risk factor contributed to the development of their disease. 

While the causes of thyroid cancer are not fully understood, there are a number of factors that can increase the risk of developing the disease.  

These factors include: 

• being female – thyroid cancer is more common in women 
• radiation exposure to the head and neck, such as childhood radiation therapy^[12] 
• a family history of thyroid disease, thyroid cancer mutations in the RET gene^[13][14] 
• certain genetic conditions, such as Carney complex type I^[15], Cowden disease^[16], familial adenomatous polyposis^[17], familial medullary thyroid cancer, familial non-medullary thyroid carcinoma^[18], multiple endocrine neoplasia type 2A syndrome, and multiple endocrine neoplasia type 2B syndrome 
• having a history of enlarged thyroid (goitre) or thyroid lumps (nodules) 
• being overweight or obese^[19][20][21]. 

If you have any of these risk factors or are concerned about your risk for thyroid cancer, please see your doctor.