Top 4 Cases of Thyroid Cancer

#1 Cause of Thyroid Cancer: Mystery

The sad truth is that for the vast majority of patients, we will never know the cause of their thyroid cancer. That said we know a lot about the underlying mechanisms that lead from a normal cell to a cancerous tumor. Some of these ideas connect the other causes of thyroid cancer so I have created a presentation to help explain some of these concepts that run through the other, less mysterious causes to thyroid cancer.

#2 Cause of Thyroid Cancer: Genetics

As we now know from the presentation above, genes play an important role in how a cell changes from a normal cell, into one that is a cause of thyroid cancer. Although in some situations a normal cell’s genetics are damaged to change it into a cancerous cell, in other cases the gene that causes thyroid cancer is inherited from a parent.

A family history of thyroid cancer in a close family member (parent, sibling or child) increases the risk of thyroid cancer, even if there is no known genetic condition, syndrome or mutation that can cause thyroid cancer in that person’s family. We know that a gene or genes is acting as a cause of thyroid cancer for such a patient, we just don’t know which gene it is.

On the other hand there are some genetic syndromes that we know are associated with genetic causes of thyroid cancer. One of the most famous genetic causes of thyroid cancer are the MEN2 (Multiple Endocrine Neoplasia) syndromes associated with mutations in the RET gene. MEN2a is associated with medullary thyroid cancer, pheochromocytoma and parathyroid adenomas. MEN2b is associated with medullary thyroid cancer, pheochromocytoma and mucosal neuromas.

Papillary thyroid cancer is the most common type of thyroid cancer, and it is associated with FAP (Familial Adenomatous Polyposis). FAP is a condition that causes many precancerous polyps to grow in the large intestine, but can also lead to other types of growths including desmoid (fibrous) tumors, stomach tumors and of course cause thyroid cancer.

Known causes of Follicular thyroid cancer include Cowden Syndrome and Carney Complex. Cowden Syndrome is associated with tumors of the breast, thyroid, uterus, colon, kidney and skin. Carney Complex is associated with brown skin spots, is a known cause of thyroid cancer as well as multiple other types of tumors in the heart, skin and endocrine system.

A relatively small proportion of thyroid cancer patients have known familial genetic disorders related to their diagnosis. That said, genetic influences that aren’t related to obvious syndromes are becoming better understood over time as more thyroid cancer related genes are identified.

#3 Cause of Thyroid Cancer: Radiation

Radiation can damage the genetics of a cell, leading to a mutation that can cause thyroid cancer. There are a number of sources of radiation that are known to cause thyroid cancer that have been well described over the years. Although most people with thyroid cancer have not been exposed to significant radiation, such exposure can increase the risk of thyroid cancer in a concerning manner. As a general rule, the younger a person is when they are exposed to radiation, and the higher the dose of radiation, the more likely that radiation is to become a cause of thyroid cancer. It is also important to point out that patients who were exposed to radiation are not more likely to have more dangerous thyroid cancers than those who were not exposed to radiation. That said, a thyroid nodule in a person who was exposed to significant radiation is more likely to be cancer than a thyroid nodule in someone with no radiation exposure.

Medical radiation is a known cause of thyroid cancer. In certain cases this medical radiation is targeted at the neck in high doses. For example, in treating Hodgkin’s lymphoma with enlarged neck lymph nodes, patients will have intentional radiation treatment of the neck that can cause thyroid cancer. In the past, before 1960, some people had low dose radiation targeted at the neck. Radiation was used to treat acne, fungal infections of the scalp, as well as enlarged tonsils and adenoids. Nowadays of course we don’t use radiation to treat these things because such radiation is a known cause of thyroid cancer and other problems.

In other situations high dose, whole body radiation is used, and the neck is of course just part of the whole body that is being radiated. This happens with bone marrow transplants and is a cause of thyroid cancer.

Certain sources of medical radiation are not significant causes of thyroid cancer. Examples include diagnostic radiation from CT scans and X-Rays in adults. Diagnostic radiation is often minimized in children to be safe, but thankfully has not been associated with a high risk of developing thyroid cancer. In adults radiation therapy targeting places other than the neck are not causes of thyroid cancer. This is because modern radiation therapy techniques are excellent at protecting the thyroid from exposure. Non-neck radiation therapy in children can be a cause of thyroid cancer later in life, such as after treatment for Wilm’s tumor or neuroblastoma.

Radiation from nuclear accidents and weapons are another known cause of thyroid cancer. After the Chernobyl disaster in 1986 there was a high rate of thyroid cancer in the area for both adults and children. This risk was reduced for children who had a high iodine content in their food, and for people of any age who took protective iodine doses at the time of the disaster.

Nuclear testing in the western states of the US has been suspected of being associated with thyroid cancer, but large scale studies have not confirmed this suspicion.

#4 Cause of Thyroid Cancer: Diet

The food we eat and the dietary habits we build up over time can affect the chances we develop thyroid cancer. There are many sources of bad information on the internet about the thyroid and diet, and it is important to stick to good research rather than getting distracted by snake oil salesmen. It is also important to note that most patients with thyroid cancer in the US do not have that cancer as a result of their diet; most have thyroid cancer for reasons that we simply do not know. That said there are two classes of dietary issues that can be causes of thyroid cancer.

Obese patients are more likely to have thyroid cancer than non-obese patients. The risk can be measured by either BMI (Body Mass Index) or by Body Fat Percentage. The risk of Papillary Thyroid cancer increases as the BMI goes up. We do not know why this is the case.

Another cause of thyroid cancer is abnormal amounts of iodine in the diet. Either too much or too little is a problem. This is very rarely an issue in the United States because we have iodine fortified foods that help avoid a deficiency, and it is rare that people in the US eat diets dominated by iodine rich foods and therefore we rarely take too much. That said, in other parts of the world, too much or too little iodine is a known cause of thyroid cancer. Too little iodine is associated with Follicular Thyroid Cancer, and too much iodine is associated with Papillary Thyroid Cancer.

Conclusion:

Although many patients have thyroid cancer for unknown reasons, there are certain causes of thyroid cancer that are known. Even though we have very little control over most of the causes of thyroid cancer, hopefully understanding these causes will help some patients understand what is happening to them, and the risks they or their families face regarding thyroid cancer.

Further Reading:

Thyroid Nodules

Thyroid Cancer Surgery

Thyroid Surgery Videos

Thyroid Cancer Symptoms