Causes, risk factors and ways to prevent thyroid cancer

The article was written by Specialist Doctor I Nguyen Thi Minh Thuyen - Pathologist, Laboratory Department - Vinmec Danang International General Hospital.

A risk factor is anything that increases a person's chances of getting the disease. Different cancers have different risks. Some risks, like smoking, can be modified. Other factors, like age or family history, cannot be changed.

Risk factors don't tell us everything. Having one or a few risk factors does not mean you will get the disease. And many people with the disease may have few or no risk factors at all. Even if a person with thyroid cancer has a risk factor, it is difficult to know how much that risk factor may contribute to cancer. Scientists have found several possible risk factors for thyroid cancer.
1. Unmodifiable risk factors 1.1. Gender and age For unknown reasons, thyroid cancer (as with most thyroid conditions) is about three times more common in women than in men.
Thyroid cancer can occur at any age, but peaks earlier in women than in men (40 or 50 in women versus 60 or 70 in men when diagnosed)
1.2. Genetic factors Several genetic factors, as well as family history, are associated with different types of thyroid cancer. However, most people with thyroid cancer have no genetic predisposition or family history of the disease.

● Medullary thyroid cancer (MTC): About 2 in 10 medullary thyroid cancers are caused by an inherited abnormal gene. These cases are called familial MTC (FMTC). FMTC may occur alone, or may be associated with other neoplasms.
The combination of FMTC and tumors of other endocrine glands (adrenal myeloma, parathyroid adenoma, ...) is called multiple endocrine neoplasia type 2 (MEN 2). mutations in the RET gene.
● Other thyroid cancers: People with certain genetic diseases are at increased risk for common types of thyroid cancer. Rates of thyroid cancer are higher in people with some less common genetic conditions such as:
Familial adenomatous polyposis (FAP): due to mutations in the APC gene, patients have many colon polyps. and have a very high risk of colon cancer, and also an increased risk of several other cancers, including papillary thyroid cancer. Cowden's disease: due to mutations in the PTEN gene, patients are at increased risk of thyroid, uterine, breast, and several other cancers. Thyroid cancer tends to be papillary or follicular. Carney syndrome, type I: due to mutations in the PRKAR1A gene, patients may have several benign neoplasms and hormone problems, as well as an increased risk of papillary and follicular thyroid cancers. Familial nonmedullary thyroid carcinoma: genes on chromosome 19 and chromosome 1 are suspected of causing these familial cancers. papillary form, and is detected at an earlier age. 1.3. Family history Having a first-degree relative (parent, sibling or child) with thyroid cancer, even if there is no hereditary syndrome in the family, also increases the risk of thyroid cancer. The genetic basis for these cancers is not entirely clear.
2. Modifiable risk factors 2.1. Radiation Radiation exposure is a proven risk factor for thyroid cancer. Emission sources include certain medical treatments (childhood radiation therapy to the head and neck, CT scans, etc.) and fallout from power plant accidents or nuclear weapons. The risk depends on the dose and the age at exposure (the higher the dose and the younger the age, the higher the risk).
2.2. Being overweight or obese According to the International Agency for Research on Cancer (IARC), people who are overweight or obese have a higher risk of developing thyroid cancer than those who do not. The risk seems to increase as body mass index (BMI) increases.
2.3. Iodine in the diet Low Iodine increases the risk of follicular thyroid cancer
Too much iodine in the diet increases the risk of papillary thyroid cancer

Thyroid cancer is associated with a number of genetic diseases, but the exact cause of most thyroid cancers remains unclear.
Certain changes in a cell's DNA (environmental, radiation, or maybe just random changes that happen inside a cell with no external cause) can cause cells to die. The thyroid gland turns cancerous.
1. Papillary thyroid cancer Several DNA mutations in the RET gene have been found in papillary thyroid cancer, called the PTC oncogene (PTC oncogene), which accounts for about 10% to 30% of all papillary thyroid cancers. papillary thyroid cancer, and has a higher incidence in children and/or is associated with radiation exposure. These RET gene mutations are found only in cancer cells and are not passed on to offspring.
Many patients with papillary thyroid cancer have mutations in the BRAF gene, which tend to grow and spread to other organs more quickly. BRAF mutations are less common in childhood thyroid cancer and in cancers that are thought to be caused by radiation exposure.
Variations in both the BRAF and RET/PTC genes are thought to cause cells to grow and divide. Very rarely, papillary cancers have mutations in both the BRAF and RET/PTC genes. Some doctors recommend testing for these gene mutations on thyroid biopsies, as they can help diagnose cancer and can also affect prognosis.
Variations in other genes are also associated with papillary thyroid cancer, including changes in the NTRK1 gene.
2. Follicular thyroid cancer Changes in the RAS oncogene (RAS oncogene) as well as changes in the PAX8-PPAR-γ rearrangement also play a role in some follicular thyroid cancers.
3. Undifferentiated thyroid cancer This type of cancer tends to have some of the same genetic mutations as in papillary and follicular cancers and often has changes in the tumor suppressor gene TP53.
4. Medullary thyroid cancer Patients with medullary thyroid cancer (MTC) have mutations in other parts of the RET gene compared with those with papillary cancer. Almost all patients with hereditary MTC and about 1 in 10 people with idiopathic (non-hereditary) MTC have a mutation in the RET gene.
Most patients with idiopathic MTC only have genetic mutations in the cancer cells. People with familial MTC and multiple endocrine neoplasia type 2 (MEN 2) inherit the RET gene mutation from their parents. These mutations are present in the body's cells and can be detected by DNA tests.

Most people with thyroid cancer have no risk factors, so the disease cannot be prevented in most cases.
Radiation exposure, especially in childhood, is a known risk factor for thyroid cancer. Because of this, doctors no longer use radiation to treat less dangerous diseases. Imaging tests such as X-rays and CT scans also expose children to radiation, but the doses are much lower, so it's not clear how much radiation can increase the risk of thyroid (or other cancers) ). If there is an increased risk the chances are small, but to be on the safe side, children should not have these tests unless they are absolutely necessary, and should use the lowest dose of radiation that will still give a clear picture. .
Genetic tests can be done to look for gene mutations in familial myeloid thyroid cancer (MTC). So most cases of familial medullary thyroid cancer can be prevented or treated early by removing the thyroid gland. When the disease is found in a family, the remaining members should be tested for the mutated gene.
When we notice abnormalities in the body, we need to go to the doctor immediately, have a general examination as well as a specialist to detect the disease as soon as possible. Doctors recommend that we go for a regular check-up once a year to understand our health status, as well as have a direction to screen for early treatment.
For thyroid cancer, we need to perform subclinical diagnostic methods such as thyroid ultrasound, cytological diagnostic tests to detect thyroid cancer.

Article referenced source: American Cancer Society