Does Hashimoto's Disease Cause Thyroid Cancer?

Hashimoto's disease is the most common cause of hypothyroidism, and thyroid cancer is the fastest rising cancer in women. Thyroid cancer sometimes occurs in patients with Hashimoto's disease, causing people to wonder if Hashimoto's disease leads to cancer.

What is Hashimoto's disease?

Hashimoto's disease (also known as Hashimoto's thyroiditis) is an autoimmune disorder. Autoimmune disorders are where the immune system attacks healthy tissues and cells. In Hashimoto's disease, your immune system makes antibodies that attack your thyroid gland.

Your thyroid gland makes hormones that regulate and control virtually all your body's metabolic functions and keep it functioning normally. Hashimoto's disease causes swelling and inflammation of the thyroid gland, which typically causes it to produce low levels of thyroid hormones.

Hashimoto's thyroiditis causes large amounts of white blood cells to accumulate in the thyroid. White blood cells are part of your body’s immune system, and when they build up, they damage the thyroid. This damage leaves it unable to produce enough thyroid hormones, a condition known as hypothyroidism.

Hashimoto's disease affects as many as 5% of all adults in Western countries. The condition occurs more frequently in women than men and is most common between 45 and 65.

What is thyroid cancer?

Cancer happens when some of the body's cells grow out of control and crowd out normal cells. These abnormal or damaged cells grow and multiply when they shouldn't, and they may form tumors. Thyroid cancer starts in the thyroid gland but may spread to other body parts, such as the lungs and bones.

The thyroid gland is composed of primarily two types of cells:

Follicular cells

Follicular cells take iodine from the blood to produce thyroid hormones. If your thyroid isn’t making the right amount of hormones, it can cause two conditions: 

Hyperthyroidism

If your thyroid produces excess hormones, it can cause a rapid or irregular heartbeat, difficulty sleeping, nervousness, increased appetite, or weight loss.

Hypothyroidism

When your thyroid produces too few hormones, your metabolism can slow down, causing you to feel tired and gain weight.

C cells

C cells are also known as parafollicular cells. They make a hormone called calcitonin, which regulates how your body uses calcium.

Different types of cancers develop from follicular cells and C cells. Many types of tumors and growths can develop in the thyroid. The cells they originate from can affect how serious the cancer is and the treatment needed.

Thyroid cancer often doesn't have any initial symptoms, but it may cause pain and swelling in your neck as it progresses. While many growths in the thyroid gland are benign (not cancerous), some are malignant, meaning they can spread to nearby tissues and other areas.

What are the types of thyroid cancer?

The four main types of thyroid cancer are:

Papillary thyroid cancer 

This is the most common thyroid cancer. It grows slowly and typically only in one thyroid gland lobe. It often spreads to the lymph nodes.

Follicular cancer 

This is the second most common type of thyroid cancer. As follicular cancer is more prevalent in iodine-deficient regions, a lack of iodine in the diet may play a role. Follicular cancers usually don’t spread to the lymph nodes, but they can spread to other parts of the body, such as the lungs or bones.

Medullary cancer

This rare form of thyroid cancer starts in the thyroid glands' C-cells.

Anaplastic cancer

This is another rare type of thyroid cancer that is very difficult to treat. It often spreads quickly into the neck and other parts of the body.

Is there a link between Hashimoto's disease and thyroid cancer?

Scientists have long recognized the link between thyroid cancer and autoimmune thyroid diseases, especially papillary thyroid cancer. While research has confirmed a link between Hashimoto's disease and thyroid cancer, the exact relationship between the two conditions is still unclear.

Research has found that the risk of developing thyroid cancer is significantly higher¹ for people diagnosed with Hashimoto's disease.  A study found that within the first three years of Hashimoto's diagnosis, the rate of thyroid cancer among patients was 30.6 per 1,000 people compared to 0.63 for people without the condition. They also found the risk of developing thyroid cancer was higher in older patients than younger patients.

These findings suggest that Hashimoto’s thyroiditis may be a pre-cancerous condition.

It is important to note that this study has limitations, as cohort studies are generally of lower quality than randomized trials.

Still, evidence supports the relationship between chronic inflammation and cancer development. One example is the link between inflammatory bowel diseases (such as Crohn’s disease and ulcerative colitis) and adenocarcinoma of the colon (colon cancer).

However, the exact connection between chronic Hashimoto’s inflammation and thyroid cancer development remains unclear and needs investigating further. 

Are there overlapping symptoms between Hashimoto's thyroiditis and thyroid cancer?

Hashimoto's thyroiditis usually progresses slowly over the years, and thyroid cancer typically doesn't produce any signs or symptoms early in the disease. While the symptoms of Hashimoto's disease can vary greatly, it does share some symptoms with thyroid cancer.

Both conditions can produce a lump that you can feel when touching your neck and noticeable swelling of the lymph nodes and thyroid. While thyroid cancer may cause pain in the neck and throat, Hashimoto's disease can also produce joint pain, muscle aches, and stiffness.

Thyroid cancer signs may also include difficulty swallowing and a noticeable change in voice, including increased hoarseness. These can also appear in Hashimoto's disease, so it’s important to speak to your healthcare provider if you’re dealing with these symptoms.

Additionally, Hashimoto’s disease may cause a wide range of symptoms, including:

• Feeling tired and sluggish

• Increased cold sensitivity 

• Dry skin

• Constipation

• Muscle weakness

• Irregular or excessive menstrual bleeding

• Depression

• Problems with memory or concentration

• A puffy face

• Brittle nails

• Hair loss

• Tongue enlargement

The diagnosis of both conditions begins with a physical exam by your doctor. Based on your examination and medical history, they will determine the appropriate tests.

Your doctor will order blood tests to check if your thyroid is functioning correctly. To identify if thyroid disease is the cause of your symptoms, your doctor will likely order blood tests to check your TSH (thyroid-stimulating hormone) and T4 (thyroxine) levels.

A TSH test checks the TSH produced by your pituitary gland. When the pituitary gland detects low thyroid hormone levels in the bloodstream, it sends TSH to tell the thyroid to increase production. High levels of TSH in the bloodstream indicate hypothyroidism.

A T4 test checks the levels of the primary thyroid hormone, thyroxine. Low levels of thyroxine with high TSH levels indicate a problem with the thyroid.

After reviewing your blood tests, your doctor will order an antibody test if they suspect Hashimoto's disease is causing hypothyroidism.

In Hashimoto's disease, the immune system typically produces an antibody that attacks thyroid peroxidase, an essential protein in thyroid hormone production. Most people with Hashimoto's disease will have thyroid peroxidase antibodies in their blood.

Your doctor may also use several other tests and procedures to diagnose thyroid cancer.

Ultrasound imaging

Ultrasound imaging uses sound waves to create pictures of body structures. 

A biopsy

During a biopsy, your doctor will use ultrasound imaging to insert and guide a long thin needle through your skin and into the thyroid nodule. Your doctor will remove a sample of suspicious thyroid tissue to analyze in the laboratory.

Other imaging tests

Your doctor may order extra imaging tests such as a CT, MRI, or nuclear imaging to determine whether cancer has spread beyond the thyroid.

When to speak to a doctor

The signs and symptoms of Hashimoto's disease vary widely and are not specific to the disorder, while thyroid cancer has few initial symptoms. However, some of the signs associated with the two conditions are similar. For example, the swelling in your throat or neck could be a symptom of either. Several conditions can cause many of these symptoms, so it's essential to talk to your doctor if you experience any signs or symptoms that concern you.

The lowdown

Hashimoto's disease and thyroid cancer are conditions that share similar symptoms, although they may be hard to detect in the early stages. While the exact relationship between the two conditions is unclear, some evidence shows that Hashimoto's disease increases a patient's risk of developing thyroid cancer.

So, if your healthcare professional has diagnosed you with Hashimoto's disease and recommends follow-ups, it’s vital to keep on top of your appointments. Be vigilant for signs of thyroid cancer to ensure that you get appropriate treatment as soon as possible.