Thyroid cancer risk factors: what raises the risk

What thyroid cancer is

The thyroid is a small, butterfly-shaped gland in the front of the neck. It makes hormones that control how the body uses energy (MedlinePlus). The main types of thyroid cancer are differentiated thyroid cancer (papillary and follicular), medullary thyroid cancer and anaplastic thyroid cancer (MedlinePlus). Papillary and follicular tumors can be treated and can usually be cured. Anaplastic tumors are less common and grow and spread quickly (NCI PDQ).

A lump in the thyroid (a nodule) is often found during a routine exam. Nodules usually do not cause symptoms or need treatment, and only a small number are diagnosed as cancer (NCI PDQ).

Risk factors

NCI lists these risk factors for thyroid cancer (NCI PDQ) (NCI PDQ screening):

• Radiation exposure. Radiation to the head and neck as an infant or child, or exposure to radioactive fallout. The cancer may occur as soon as 5 years after exposure (NCI PDQ). MedlinePlus also names radiation from a radiation emergency (MedlinePlus).
• A history of goiter (enlarged thyroid) (NCI PDQ).
• A family history of thyroid disease or thyroid cancer (NCI PDQ).
• Certain genetic conditions, such as familial medullary thyroid cancer (FMTC) and multiple endocrine neoplasia type 2A or 2B (MEN2A, MEN2B) (NCI PDQ).
• Being female (NCI PDQ).
• Being between 25 and 65 years old (NCI PDQ).
• Being Asian (NCI PDQ).

Having a risk factor does not mean you will get cancer, and not having risk factors does not mean you will not. NCI advises talking with your doctor if you think you may be at risk (NCI PDQ).

Inherited medullary thyroid cancer

Medullary thyroid cancer starts in the C cells of the thyroid, which make the hormone calcitonin (NCI PDQ). It is sometimes caused by a change in the RET gene that is passed from parent to child (NCI PDQ).

A genetic test can check for the changed gene. If a patient has it, other family members may be tested too. Family members, including young children, who have the changed gene may have surgery to remove the thyroid, which can lower the chance of developing medullary thyroid cancer (NCI PDQ).

Signs to check with a doctor

Thyroid cancer may not cause early signs. It is sometimes found during a routine physical exam, and signs may appear as the tumor grows. Other conditions can cause the same signs. Check with your doctor if you have (NCI PDQ) (MedlinePlus):

• a lump (nodule) in the neck
• trouble breathing
• trouble swallowing
• pain when swallowing
• hoarseness or other voice changes that do not get better

Screening

NCI says there is no standard or routine screening test for thyroid cancer, and studies have shown that screening does not lower the chance of dying from it (NCI PDQ screening). For what the US Preventive Services Task Force says about screening adults without symptoms, see the thyroid cancer screening check.

Thyroid cancer is different from an underactive or overactive thyroid; for that, see the thyroid function (TSH) screening check. All cancer checks are on the cancer screening hub.

Common questions

Is thyroid cancer genetic?

Sometimes. A family history of thyroid disease or thyroid cancer raises the risk, and medullary thyroid cancer is sometimes caused by an inherited change in the RET gene, as in MEN2 syndromes (NCI PDQ).

Should I get a thyroid ultrasound to check for cancer?

Neck exams and ultrasound are sometimes used to screen for thyroid cancer, but NCI says they do not lower the risk of dying from it (NCI PDQ screening). If you have a neck lump or another sign above, see your doctor; the thyroid cancer screening check covers screening for people without symptoms.

Is a thyroid nodule cancer?

Usually not. Only a small number of thyroid nodules are diagnosed as cancer. An ultrasound and a fine-needle biopsy are often done to check (NCI PDQ).