Risks And Causes Of Thyroid Cancer
A persons risk of developing thyroid cancer depends on many factors, including age, some non cancerous thyroid conditions and a family history of thyroid cancer.
We dont know what causes most thyroid cancers. But there are some factors that might increase your risk of developing it.
Having any of these risk factors doesnt mean that you will definitely develop thyroid cancer.
Demographic And Clinical Features
Figure 1 presents the flowchart for the identification of three cohorts of FTC patients according to the status of distant metastasis, including metastasis identified at presentation , metastasis identified during the follow-up period , and no evidence of metastasis . A total of 460 patients with FTC were identified in our thyroid cancer registry dataset at Chang Gung Memorial Hospital in Taiwan between December 1976 and May 2020. Patients were excluded if they met the exclusion criteria, including 66 patients who had initial surgery at other hospitals, 48 who were lost to follow-up, 20 who had initial surgery at other hospitals and also lost to follow-up, 130 who had missing data identified during the validation process using electronic health record, and 6 with local recurrence and without metastasis. Therefore, 190 patients with FTC diagnosed between August 1987 and July 2018 were included for further analysis, including 29 in the M1 group, 14 in the M2 group, and 147 in the M0 group.
Flowchart of cohort establishment.
Radiation Therapy And Radiation Exposure
People who undergo radiation therapy in infancy or childhood for conditions such as an enlarged thymus, tonsils, or adenoids may develop thyroid cancer. According to experts, cancer can develop as early as 5 years after radiation therapy or 20 or more years later.
Exposure to radiation from nuclear fallout is also associated with a high risk of thyroid cancer, especially in children.
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Estrogen And Reproductive Factors
Estrogen has historically been proposed as a potential mechanism mediating the risks of breast cancer , endometrial cancer , and ovarian cancer . Given that women account for over three-fourth of the prevalence of thyroid cancer, estrogen is regarded as a possible risk factor . The exposure to exogenous estrogen has also seen an increasing trend due to various medical and environmental sources, including oral contraceptives, hormone replacement therapy, and consumption of meat from animals treated with growth hormone. Evidence linking these to thyroid cancer risk is, however, nonconclusive.
Cellular studies have shown that estrogen and its receptors play an important role in the proliferation, migration, and invasion of thyroid cancer . It exerts its growth-promoting effect via a membrane-bound estrogen receptor . ER activation seems to induce the development of thyroid cancer, while wild-type ER plays a protective role against thyroid cancer . However, such effects or pathways have not been successfully demonstrated in human studies.
Worldwide Increasing Incidence Of Thyroid Cancer: Update On Epidemiology And Risk Factors
Gabriella PellegritiAcademic Editor: Received
Background. In the last decades, thyroid cancer incidence has continuously and sharply increased all over the world. This review analyzes the possible reasons of this increase. Summary. Many experts believe that the increased incidence of thyroid cancer is apparent, because of the increased detection of small cancers in the preclinical stage. However, a true increase is also possible, as suggested by the observation that large tumors have also increased and gender differences and birth cohort effects are present. Moreover, thyroid cancer mortality, in spite of earlier diagnosis and better treatment, has not decreased but is rather increasing. Therefore, some environmental carcinogens in the industrialized lifestyle may have specifically affected the thyroid. Among potential carcinogens, the increased exposure to medical radiations is the most likely risk factor. Other factors specific for the thyroid like increased iodine intake and increased prevalence of chronic autoimmune thyroiditis cannot be excluded, while other factors like the increasing prevalence of obesity are not specific for the thyroid. . The increased incidence of thyroid cancer is most likely due to a combination of an apparent increase due to more sensitive diagnostic procedures and of a true increase, a possible consequence of increased population exposure to radiation and to other still unrecognized carcinogens.
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Risk Factors For Cancer
We sought to identify risk factors for cancer-specific mortality in these 190 FTC patients . Univariate Cox regression analysis revealed that cancer-specific mortality was significantly correlated with old age , metastasis , advanced TNM stage , extrathyroidal invasion , 131I cumulative dose â¥100 mCi , and EBRT . In a multivariate Cox regression analysis adjusted for age, gender, T stage, N stage, M stage, extrathyroidal invasion, primary surgery, 131I cumulative dose, EBRT, and targeted therapy, only distant metastasis was significantly associated with increased risk of cancer-specific mortality .
Radiation Exposure From Atomic Bombing Nuclear Accidents And From Nuclear Facilities In The Past
Numerous studies indicated the serious health consequences of the atomic bombing in Hiroshima, Nagasaki, Nevada, Marshall Islands, Semipalatinsk, Nowaja Semlja.58–61) Thyroid cancer was among the first solid cancers that arose after the atomic bombing in Japan.59,60) The highest risk of thyroid cancer was among of atomic bombs survivors in Hiroshima and Nagasaki younger than 10 years old, in the older subjects the risk was considerably smaller.61)
The consequences of exposure from fallout after the Russian nuclear tests in Nowaja Semlja and the incidence of thyroid cancer were studied in Norway and Sweden by Lund and Galanti.62) The authors found that the RR of developing thyroid cancer was higher for exposed cohorts , compared to ones not exposed .
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What Increases Your Chances Of Developing This Disease
Though the is unknown, there are risk factors that may raise your risk of developing the disease.
There are 4 main types of , with being the most common. Having any of the risk factors listed below may increase the likelihood that you will develop any form of thyroid cancer, including papillary thyroid cancer:
A family history of thyroid cancer
A personal or family history of
Whole-body radiation for bone marrow treatment
Exposure to high levels of radiation caused by nuclear accidents or weapons testing
Having a personal or family history of certain genetic syndromes, such as Cowden syndrome
Though the primary risk factors for thyroid cancer generally span across the 4 types, some are unique to papillary thyroid cancer. First, papillary thyroid cancer is more common in women than in men. So being a woman is considered a risk factor.
Also, people under the age of 50 are more likely to develop papillary thyroid cancer, with people aged 30 to 50 at the highest risk. That, however, doesn’t mean older adults can’t develop the disease. In fact, adults over the age of 50 tend to have more aggressive forms of papillary thyroid cancer, though they have a lower chance of developing it.
Papillary thyroid cancer is very curableespecially if you are diagnosed early. That’s why it’s important to talk to your doctor if you have any of these risk factors. People who are at a higher risk for developing papillary thyroid carcinoma should be regularly checked for suspicious .
Exposure To Ionizing Radiation Exposure To Ionizing Radiation Is The Strongest Risk Factor For Thyroid Cancer The Risk Of Developing Thyroid Cancer Is Related To Your Age When You Were Exposed The Younger You Are When Exposed To Radiation The Greater The Risk Of Developing Thyroid Cancer
People, especially children, who receive radiation therapy to the head and neck have a higher risk of developing thyroid cancer. When thyroid cancer develops, it usually occurs 20 to 40 years after the radiation exposure. The risk of developing thyroid cancer after radiation therapy depends on the type of radiation used and the dose. The benefit of treating a cancer usually outweighs the risk of developing thyroid cancer later in life.
People who received low-dose radiation as children to treat non-cancerous conditions like fungal infections of the scalp, acne or enlarged tonsils have an increased risk of developing thyroid cancer.
Nuclear accidents and weapons
People who are exposed to ionizing radiation from nuclear accidents or weapons have a greater risk of developing thyroid cancer, especially if they were children when they were exposed to the radiation.
Diagnostic imaging tests
Diagnostic imaging tests, such as x-rays and CT scans, use ionizing radiation to make images. There is some evidence that having diagnostic imaging tests may increase the risk for thyroid cancer. The risk of cancer from imaging tests must be weighed against their benefits. Modern imaging equipment delivers the lowest amount of radiation possible.
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Sporadic Medullary Thyroid Cancer
Sporadic medullary thyroid cancer comes from the C cells of your thyroid gland. These cells make a hormone that controls the amount of calcium in your blood.
Between of medullary thyroid cancers are sporadic, meaning they arent hereditary. Sporadic medullary thyroid cancer occurs mainly in older adults.
If diagnosed in stages I through III, MTC can have a good outlook.
Risk Factors For Incidental Thyroid Cancer
All histological types
Although MNG histological type, histopathological diagnosis and preoperative disease duration were identified as significant risk factors for thyroid cancer in univariable analysis , they failed to reach statistical significance in multivariable regression analysis.
Increasing thyroid functional status was associated with a decreasing cancer rate , with hyperthyroidism demonstrating the lowest risk of cancer , followed by euthyroidism the highest risk was observed in hypothyroid patients . Older age was correlated significantly with a decreased cancer rate , as was female sex , with men demonstrating a 27.5 per cent increased risk of cancer. HT and CNST were also strongly associated with thyroid cancer. In addition, larger size adenomas were correlated with a decreased rate of cancer, compared with smaller adenomas . The multivariable analysis for each group of patients is depicted in .
Multivariable logistic regression analysis of parameters significantly associated with all histological types of thyroid cancer, papillary thyroid cancers, papillary thyroid microcarcinoma and Hürthle cell thyroid cancer
Papillary thyroid cancer
Papillary thyroid microcarcinoma
Hürthle cell cancer
Increasing thyroid functional activity was associated with a decreasing HCC rate . Unlike for other histological types, older age was a significant risk factor for HCC .
Total or near-total thyroidectomy
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Nitrate And Radiation As Possible Interacting Carcinogens
Besides the radiation exposure, nitrates are discussed as a risk factor for developing thyroid cancer.129–131) Environmental endocrine effects caused by nitrates have received increasing attention over the last 15 years. Nitrate can interfere with steroid and thyroid hormone homeostasis, reproductive and developmental endpoints as environmental endocrine disruptor.132) Over the past hundred years, human activity through the use of nitrate fertilizers and the combustion of fossil fuels have doubled the natural nitrogen level onto land.129,133–135) In the United States the maximum contaminant level of public drinking water for nitrate is 10 mg/L as nitrate-nitrogen . In accordance with the World Health Organization guideline, nitrate standards for drinking water are 50 mg/L as NO3 or 11.3 mg/L NO3-N. These nitrate regulations have been developed for the prevention of infant methemoglobinemia however cancer and other adverse health consequences were not considered.129)
Orita et al.139) performed in Kawauchi village an examination of nitrate concentrations in drinking water. The average nitrate-N level was 0.62 mg/L , which was in the normal range.139) The authors concluded that the examinations of dietary nitrate intake also are required for better understanding of the situation with the increased incidence of thyroid cancer in Fukushima.139)
We thank Prof. Peter Kopp for a critical review with fruitful discussions and valuable comments and suggestions.
Reducing Your Risk And Other Possible Causes
You might have heard of other possible causes of cancer. Stories about potential causes are often in the media and it isnt always clear which ideas are supported by evidence.
We havent included them here, either because there is no evidence about them or it is less clear.
A pooled analysis of thyroid cancer incidence following radiotherapy for childhood cancer LHS Veiga and others
Cancer. Principles and practice of oncology VT De Vita, S Hellman and SA RosenbergLippincott, Williams and Wilkins, 2018
The fraction of cancer attributable to known risk factors in England, Wales, Scotland, Northern Ireland, and the UK overall in 2015KF Brown and othersBritish Journal of Cancer, 2018. 118, Pages 1130-1141
Family History of Cancer and Risk of Sporadic Differentiated Thyroid Carcinoma
L Xu and others
Papillary thyroid cancer: Clinical features and prognosis
R Tuttle and others
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Risk Factors For Thyroid Cancer
A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. But sometimes thyroid cancer develops in people who dont have any of the risk factors described below.
Thyroid cancer can develop at any age, but most cases occur in people 20 to 55 years of age. More women than men develop thyroid cancer.
Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.
Having Had Cancer Before
Some studies suggest that people treated as adults for certain cancers have an increased risk of thyroid cancer. These include:
- non-Hodgkin lymphoma
- cancer of the food pipe
- testicular cancer
It is not known if this is due to treatment for these cancers, common risk factors or inherited genetic changes. In the case of oesophageal cancer, it may be because routine checks after treatment pick up the thyroid cancers.
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What Is The Thyroid
The thyroid gland is located in front of the neck. It looks sort of like a butterfly with one wing on each side of the neck. The thyroid is important in many ways for keeping your body healthy. It sends out certain chemicals that help control many activities in the body, such as breathing and pumping blood. The thyroid helps childrens bodies develop as they grow up, including getting taller and putting on muscle. It helps control weight and is also involved in other functions.
Not Enough Iodine In Your Diet
Iodine is a mineral found in some foods. Your body needs it to make thyroid hormones. Certain thyroid cancers are more common in parts of the world where people have low levels of iodine. In some countries, including the U.S., iodine is added to table salt and other foods to help give you a boost.
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Non Cancerous Thyroid Disease
Some non cancerous conditions of the thyroid increase your risk of thyroid cancer. These include:
- an enlarged thyroid
- a condition where the immune system attacks the thyroid gland
Its important to remember that although having a lump or nodule increases the risk, thyroid cancer is rare. Thyroid lumps are common. But only about 5 out of 100 thyroid lumps are cancer.
Familial Medullary Thyroid Carcinoma
Around two out of 10 cases of medullary thyroid cancer are due to inheriting a mutated gene. When this occurs, it’s known as familial medullary thyroid carcinoma . In these cases, the thyroid cancer can appear by itself or it may occur along with other tumors.
When FMTC occurs with other tumors, this is known as multiple endocrine neoplasia type 2 .
Both FMTC and MEN 2 are inherited and are caused by mutations in the RET gene. We all inherit two copies of each gene, one from each parent. If you have a RET mutation, this typically means that one copy of the RET gene you inherit is mutated. With either FMTC or MEN 2, cancer typically develops in childhood or young adulthood.
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How Is Thyroid Cancer Prevented
In most cases, the cause of thyroid cancer isnt known, which means that theres no known way to prevent it for many people.
Medullary thyroid cancer can be hereditary, so its best to talk to a doctor if your family has a history of this type of thyroid cancer. The doctor can refer you to a genetic counselor who can determine how likely you are to develop thyroid cancer.
Increased Use Of Imaging Examination
Thyroid nodules are found in 30%50% of the population in late adulthood . Therefore, incidental thyroid nodules are frequently identified upon physical examination or diagnostic procedures for other primary diseases. In the past 30 years or so, the advancement in imaging technology has made possible the identification of many previously undetectable conditions via the use of imaging modalities.
Individuals reportedly underwent an average of 1.18 imaging studies per year in the U.S. . Of all the imaging scans, 35% were advanced diagnostic imaging studies such as computed tomography , magnetic resonance imaging , ultrasound, or nuclear medicine, including positron emission tomography . Over the 15 years of the study, imaging rates for CT scans increased 8% annually. During 2004 to 2010, MRI rates increased 10%, ultrasound 4%, and PET scans 57%, annually. In the U.S. study of the thyroid cancer epidemic and density of endocrinologists, the incidence rates were also found to be significantly correlated with the use of cervical ultrasonography in both males and females . It is likely that increased use of imaging examination had led to the identification of an increasing number of otherwise clinically occult thyroid diseases.
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Demographic And Clinical Features Of 14 Patients Developed Metastasis During Follow
A total of 14 patients developed distant metastasis during follow-up . The median time from FTC diagnosis to distant metastasis was 9.6 years . There were four male and ten female patients aged between 38 and 70 years. The median size of FTC was 4.0 cm . The initial TNM stages were categorized into I , II , III , and IV . There were 4 patients with extrathyroidal invasion of tumor during operation. Most patients received a total thyroidectomy at diagnosis of FTC, and all underwent radioiodine treatment with a median cumulative dose of 380 mCi . The primary sites of metastasis were the lung , followed by bone . Three patients developed lung and bone metastases sequentially. Of the 12 patients with lung metastasis, 3 underwent surgery for lung lesions. Of the 5 patients with bone metastasis, 4 received palliative EBRT for bone lesions. One patient received targeted therapy . Four patients died of FTC, including those 3 patients developing both lung and bone metastases.