Understanding How Common Thyroid Cancer Is

Thyroid cancer is not as common as other major cancers, but it remains the most frequent type of cancer affecting the endocrine system. In the United States, around 44,000 people receive a new thyroid cancer diagnosis each year, which is a much smaller number compared to over 280,000 cases of breast cancer or more than 150,000 cases of colon cancer diagnosed annually.^[5] Despite this lower incidence, approximately 2,000 patients die from thyroid cancer every year.^[5]

Women are affected far more often than men. In fact, women are three times more likely to develop thyroid cancer compared to men.^[2] The disease is commonly diagnosed in women during their 40s and 50s, while men are more likely to be diagnosed in their 60s and 70s.^[2] Although thyroid cancer can occur at any age, it is often diagnosed at a younger age than most other adult cancers. Even children can develop the disease, though this is rare.^[7]

Over the past few decades, the number of people diagnosed with thyroid cancer has increased worldwide. This rise is largely attributed to advances in imaging technology and medical equipment, such as ultrasounds, computed tomography scans, magnetic resonance imaging, and other diagnostic tools that can detect small thyroid nodules incidentally during exams for unrelated conditions.^[4] This means many cases are now discovered earlier, often before any symptoms appear, which may explain the upward trend in diagnosis rates even as the mortality rate has remained relatively stable.^[4]

What Causes Thyroid Cancer

The exact cause of thyroid cancer remains unknown in most cases. Scientists have identified certain genetic changes that can trigger the disease, but these changes do not always have a clear origin. When cells in the thyroid undergo changes to their DNA, they can begin to grow and multiply uncontrollably. Unlike healthy cells, which die naturally, these abnormal cells continue to accumulate and eventually form a tumor.^[1]

Genetic mutations play a significant role in the development of thyroid cancer. Mutations in genes that are part of the mitogen-activated protein kinase (MAPK) cellular signaling pathway—a system that helps control cell growth—have been implicated in most thyroid cancers.^[4] For example, a point mutation in the BRAF gene, known as BRAF V600E, is the most common mutation found in papillary thyroid cancer, occurring in 29 to 69 percent of cases.^[4] Other genetic changes, such as translocations involving the RET gene or mutations in the RAS proto-oncogene, are also found in various types of thyroid cancer.^[4]

In some instances, thyroid cancer runs in families. Approximately 5 percent of papillary and follicular thyroid cancer cases and 15 to 30 percent of medullary thyroid cancer cases are linked to a family history of the disease.^[4] Medullary thyroid cancer can be caused by inherited genetic mutations, such as changes in the RET proto-oncogene, which are passed from parent to child.^[6] Genetic testing is recommended for all patients with medullary thyroid cancer to determine whether these hereditary changes are present, as this information can help guide treatment and screening for family members.^[7]

Groups and Factors That Increase Risk

While the exact cause of thyroid cancer is often unclear, certain factors can increase a person’s likelihood of developing the disease. One of the most significant risk factors is exposure to high levels of radiation, particularly to the head, neck, or chest. This exposure can occur through radiation therapy used to treat other cancers, such as lymphoma or breast cancer, or through environmental events like nuclear accidents or atomic bomb exposure.^[1] Before 1960, some individuals even received low-dose radiation treatments for non-cancerous conditions affecting the skin, scalp, or tonsils, which increased their risk later in life.^[22]

Radiation exposure is particularly harmful when it occurs during childhood or adolescence, as the thyroid gland is more vulnerable during these developmental stages. People who work in certain professions, such as x-ray technicians or fluoroscopy technicians, may also be at higher risk if they are repeatedly exposed to radiation without adequate protection.^[22] Wearing a thyroid shield during radiation exposure can help reduce the risk.^[22]

A family history of thyroid cancer is another important risk factor. If a close family member, such as a parent, sibling, grandparent, or child, has had thyroid cancer, the risk of developing the disease increases, even if there is no known genetic mutation or syndrome present.^[1] Individuals with a first-degree relative who has had papillary thyroid cancer face a 2 to 10 times higher risk of developing the same type of cancer.^[22] In families with medullary thyroid cancer, inherited genetic syndromes like Multiple Endocrine Neoplasia (MEN2) are more common, and genetic testing can identify these risks early.^[22]

Age and sex also play a role. While thyroid cancer can occur at any age, the majority of cases are diagnosed in people over 40, although it affects all age groups from children to seniors.^[7] Women are disproportionately affected, being three times more likely than men to develop the disease.^[7]

How Thyroid Cancer Presents Itself

Many people with thyroid cancer do not experience obvious symptoms in the early stages of the disease. As a result, most individuals are unaware they have cancer until a healthcare provider detects a lump or swelling during a routine physical examination. This lump, called a thyroid nodule, is an abnormal growth of thyroid cells that can sometimes be felt when a doctor palpates the neck.^[6] It is important to note that most thyroid nodules are not cancerous. Only about 3 out of 20 thyroid nodules turn out to be malignant.^[6]

When thyroid cancer does cause symptoms, they often include a noticeable lump or swelling in the front of the neck, particularly below or near the larynx, where the thyroid gland is located.^[2] As the cancer progresses, additional symptoms may develop, such as hoarseness or difficulty speaking, which can occur if the cancer affects the vocal cords or nearby nerves. Swollen lymph nodes in the neck are another sign, as papillary thyroid cancer often spreads to these glands.^[2]

In more advanced stages, patients may experience difficulty swallowing or breathing, as the growing tumor can press against the esophagus or windpipe. Pain in the throat or neck is also possible, though less common.^[7] If the cancer has spread to other parts of the body, symptoms such as tiredness, loss of appetite, nausea, vomiting, and unexpected weight loss may occur.^[2]

Despite the presence of a thyroid nodule, many people with thyroid nodules do not have symptoms related to the nodule itself. Thyroid nodules usually do not interfere with the normal function of the thyroid gland, meaning that hormone levels remain balanced and the body continues to regulate metabolism, body temperature, heart rate, and blood pressure normally.^[6]

Ways to Lower Your Risk

There is no standard or routine screening test for thyroid cancer, and because the disease is not linked to lifestyle factors like diet, smoking, or alcohol use, traditional prevention strategies such as dietary changes or exercise do not directly reduce the risk of developing thyroid cancer.^[18] However, there are steps individuals can take to minimize their risk or ensure early detection.

Minimizing radiation exposure is one of the most important prevention measures. People who require radiation therapy for other cancers should discuss the use of thyroid shields with their healthcare team to protect the thyroid gland from unnecessary exposure.^[22] Those who work in medical or industrial settings where radiation is present should consistently wear protective equipment, such as thyroid shields, and monitor their exposure using a dosimeter, a device that tracks radiation levels.^[22] Parents should also inquire about minimizing radiation exposure for children undergoing diagnostic imaging, as the thyroid gland is more sensitive during early developmental years.^[22]

Knowing your family history is another key prevention strategy. If you have a close family member who has been diagnosed with thyroid cancer, inform your doctor, as this increases your risk. In cases of medullary thyroid cancer, genetic testing can identify inherited mutations that predict the development of the disease. For individuals with these genetic changes, preventive removal of the thyroid gland during childhood may be recommended, as it has a high probability of being curative.^[7]

Regular medical check-ups that include a physical examination of the neck can help detect thyroid nodules early. While most nodules are benign, finding them early allows for timely evaluation and, if necessary, further testing to rule out cancer.^[18] Early diagnosis significantly improves outcomes and reduces the likelihood of the cancer spreading to other parts of the body.^[14]

How the Body Changes With Thyroid Cancer

The thyroid gland plays a vital role in regulating many of the body’s essential functions. Located at the base of the throat near the windpipe, this small, butterfly-shaped gland produces hormones that control metabolism, body temperature, heart rate, and blood pressure.^[6] When thyroid cancer develops, the normal functioning of the thyroid can be disrupted, although in many cases, especially with small cancers, thyroid function is preserved.^[10]

Thyroid cancer begins when normal thyroid cells undergo changes that cause them to grow and divide uncontrollably. Instead of dying as healthy cells do, these abnormal cells continue to accumulate and form a tumor.^[1] In some cases, these cancer cells invade nearby tissues, such as the muscles, nerves, or esophagus in the neck. Thyroid cancer, particularly papillary thyroid cancer, often spreads to the lymph nodes in the neck, which are small glands that help fight infection.^[2]

More aggressive types of thyroid cancer, such as follicular thyroid cancer, can spread through the bloodstream to distant organs, including the lungs and bones. This process, known as metastasis, occurs when cancer cells break away from the original tumor and travel to other parts of the body.^[5] Anaplastic thyroid cancer, the rarest and most aggressive form, grows and spreads quickly, making it harder to treat.^[2]

The size and location of the tumor can affect how the body functions. Larger thyroid nodules may press against the trachea or esophagus, causing difficulty breathing or swallowing. If the cancer affects the nerves near the vocal cords, hoarseness or changes in voice may result.^[2] When cancer spreads to the lymph nodes, they may become swollen and palpable during a physical examination.^[2]

In cases where thyroid cancer requires surgical removal of the thyroid gland, the body loses its ability to produce thyroid hormones naturally. These hormones are essential for maintaining energy levels, regulating body temperature, and supporting the function of the heart, brain, and other organs. Without a thyroid, patients must take daily thyroid hormone replacement medication to compensate for the missing gland.^[12] This lifelong treatment ensures that the body continues to function normally and can also help prevent the cancer from returning by suppressing the production of thyroid-stimulating hormone (TSH), which can encourage the growth of any remaining cancer cells.^[7]