Causes of thyroid cancer
We do not yet know what causes thyroid cancer in most people, but some things may increase the risk of developing it.
What causes thyroid cancer?
The causes of thyroid cancer in most people are not known. But there are some things that may increase your risk of developing it. These are called risk factors. Having 1 or more risk factors does not mean you will get thyroid cancer. And if you do not have any risk factors, it does not mean you will not get cancer.
The information here is about papillary and follicular thyroid cancers. Medullary thyroid cancer and anaplastic thyroid cancer have different risk factors.
If you are worried about thyroid cancer and would like to talk to someone, we are here. You can:
- Call the Macmillan Support Line on 0808 808 00 00.
- Chat to our specialists online.
Related pages
Age
In women and people assigned female at birth the rates of thyroid cancer are highest in the early 40s. In men and people assigned male at birth the highest rates are in the early 70s.
Papillary thyroid cancer can also affect teenagers and young people in their 20s.
Sex
Thyroid cancer is much more common in women and people assigned female at birth. There might be links to female hormones, and factors such as when periods or menopause started, or pregnancy.
Non-cancerous thyroid disease
Having an overactive or underactive thyroid (hyperthyroidism and hypothyroidism) does not increase the risk of developing thyroid cancer. Some types of non-cancerous (benign) thyroid disease can slightly increase the risk of thyroid cancer. These include:
- an enlarged thyroid (goitre)
- thyroid nodules (adenomas)
- inflammation of the thyroid (thyroiditis) – including Hashimoto’s thyroiditis.
Thyroid goitres and nodules are common. But they are not usually cancerous. Sometimes a nodule might be found during a scan that is done for another condition.
Benign thyroid disease can run in families. You are more at risk of getting thyroid cancer if you have family members with benign thyroid disease.
Related pages
Exposure to radiation
Having had radiotherapy to the head or neck area, usually in childhood, can increase the risk of developing thyroid cancer many years later. Being exposed to high levels of radiation in the environment can also increase your risk. For example, accidental exposure after a nuclear accident. This is very rare.
It is important to remember that only a small number of thyroid cancers are caused by any kind of radiation exposure.
Family history
Your risk of developing thyroid cancer might be higher if you have a close family member (relative) with thyroid cancer. A close relative is:
- a parent
- a brother or sister (sibling)
- your child.
If you have more than 1 close relative affected and especially if they had cancer at a young age, the risk is higher. The risk is still small because thyroid cancer is rare.
Related pages
Inherited genetic conditions
Having a rare genetic condition called familial adenomatous polyposis (FAP) might slightly increase the risk of papillary thyroid cancer.
FAP and another rare genetic condition called multiple endocrine neoplasia type 2 (MEN2) increase the risk of medullary thyroid cancer.
People with PTEN Hamartoma tumour syndrome have a higher risk of thyroid cancer. This is a group of rare conditions which include Cowden’s syndrome. PTEN UK and Ireland has more information.
Weight
Being overweight may increase the risk of getting thyroid cancer. A healthy diet and regular exercise may reduce the risk.
About our information
This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer.
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References
Below is a sample of the sources used in our thyroid cancer information. If you would like more information about the sources we use, please contact us at
informationproductionteam@macmillan.org.uk
National Institute for Health and Care Excellent (NICE). [NG230]. Thyroid cancer: assessment and management. Published: 19 December 2022. Available from: www.nice.org.uk/guidance
Datta, R. British Medical Journal Best Practice Guidelines, Thyroid cancer. 2023. British Medical Journal. Available from: www.bestpractice.bmj.com/topics/en-gb/263
European Society Medical Oncology (ESMO): Thyroid cancer, Clinical Practice Guidelines for Diagnosis, Treatment and Follow-up. 2019. Available from: www.annalsofoncology.org/article/S0923-7534(20)32555-2/fulltext
Date reviewed
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