Hashimoto’s Thyroiditis And Crohn’s Disease: Is There A Connection?

Hashimoto's disease is an autoimmune disease of the thyroid, and Crohn's is an inflammatory bowel disease. Both of these diseases are impacted by the immune system. In this article, we'll learn more about the two diseases, and explore the science of the connection between the two.

What is Hashimoto's disease?

Hashimoto's disease is an autoimmune disease. When you develop an autoimmune disease, your body's immune system turns on you, mistakenly attacking parts of your body that are not actually doing any harm.

There are autoimmune diseases that affect almost every part of the body. The thyroid gland can be affected by two autoimmune disorders: Graves' disease and Hashimoto's disease.

With Hashimoto's disease, the immune system's attack on the thyroid causes it to weaken, rendering it incapable of producing enough thyroid hormones for your body. This is a condition known as hypothyroidism or underactive thyroid.

Risk factors

The exact causes of Hashimoto's aren't known, but we have reliable data on the type of people who are most likely to develop the disease. Familiarizing yourself with the risk factors will help you provide relevant information to your doctor if you develop any of the symptoms. This is particularly useful, as none of the symptoms are unique to Hashimoto's disease; they include:

Genetics

A number of genetic factors can increase your chances of developing Hashimoto's disease. If someone in your family has had the disease, then you are at an increased risk of getting it as well. Several genes have been shown¹ to increase one's susceptibility to Hashimoto's thyroiditis.

Being female

Women are more likely than men² to develop Hashimoto's thyroiditis, especially those who are middle-aged. This is believed¹ to be partly due to the extra X chromosome that women have. The X chromosome contains several genes that are important for proper immune function.

Excessive iodine levels

Because iodine plays an important role in thyroid function, excessive iodine intake is connected to Hashimoto's.  One study¹ showed a direct link between iodine consumption and the development of Hashimoto's disease.

Exposure to radiation

An environmental factor that can increase the risk of Hashimoto's disease is radiation exposure.³ The risk is the same when the exposure is from catastrophic events, such as nuclear fallout, or common sources, such as medical radiation.

Other autoimmune diseases

Having another autoimmune disease also increases the risk of developing Hashimoto's, and vice-versa. These include disorders⁴ such as celiac disease, lupus, rheumatoid arthritis, and type 1 diabetes.

Symptoms

Many people with Hashimoto's disease initially have no symptoms and can often go for years without knowing that they have the condition. As the disease takes its toll on the thyroid, symptoms of hypothyroidism will begin to appear.

The symptoms of hypothyroidism vary from person to person. Some of the most common include:

• Unexplained weight gain

• Intolerance to cold

• Decreased heart rate

• Pain in the joints or muscles

• Irregular menstrual periods

• Fertility problems

• Dry skin

• Thinning hair

• Depression

• Fatigue

Potential complications

Because the disease weakens the thyroid gland, hypothyroidism is the most common complication. One of the rare but life-threatening complications of untreated hypothyroidism is myxedema coma.⁵

This condition results from hypothyroidism becoming bad enough to slow the thyroid's functions to the point of being able to cause death. Myxedema coma won't necessarily render people comatose, but it is a medical emergency.

Hypothyroidism can affect ovulation and make it more difficult to conceive. It can also lead to an increased risk of birth defects⁶ when untreated during pregnancy. These include heart problems, additional fingers, and/or a cleft palate.

An underactive thyroid can increase the level of bad cholesterol. When too much bad cholesterol is in your system, it can lead to a hardening of the arteries. This increases your risk of both heart attack and stroke.

Hypothyroidism can also make it more difficult for the heart to pump blood, by causing a buildup of fluid around the heart.

The condition is also known to cause depression that can worsen as the condition does.

Treatment

If your Hashimoto's thyroiditis leads to hypothyroidism, your doctor will likely put you on levothyroxine, which is a drug that's identical to the hormones produced by the thyroid. Regular blood tests to monitor your hormone levels are required to ensure that you are on the right dosage. Your doctor may also recommend diet and lifestyle changes.

What is Crohn's disease?

Crohn's disease is a type of inflammatory bowel disease (IBD) characterized by the inflammation of the gastrointestinal tract.

Risk factors

Like Hashimoto's, the exact causes of Crohn's disease remain a mystery. However, there are a number of factors that show up more commonly in Crohn's patients than in the general population. Experts believe these factors may play a role in the development of the disease:

Genetics

Crohn's disease can be hereditary. Those who have a parent, sibling, or child with Crohn's disease are also at increased risk of developing it. Research has discovered some of the genes responsible⁷ for Crohn's.

Age

While Crohn's disease doesn't exclusively affect people of any age range, young people are more likely⁷ to get the condition. The most common age range is between 15 and 35.

Smoking

Those who smoke double⁸ their risk of developing Crohn's disease. Smokers also have worse outcomes when they do get Crohn's. It's important for Crohn's patients to stop smoking.

Nonsteroidal anti-inflammatory drugs (NSAIDs)

These drugs include aspirin, ibuprofen, antibiotics, and some birth-control pills. People who take them have a slightly higher risk of developing Crohn's.

Diet

Research shows that eating a diet that's high in fat can cause a slight increase in the chances of a person developing Crohn's disease.

Symptoms

The symptoms of Crohn's disease can vary in intensity. Flare-ups of the disease may make symptoms worse. The symptoms most commonly associated with Crohn's disease are:

• Diarrhea

• Pain or cramping in the abdomen

• Weight loss

• Fatigue

• Anemia

• Pain or soreness in the joints

• Redness or pain in the eyes

• Nausea

• Loss of appetite

Potential complications

In addition to the potential for severe flare-ups of the symptoms mentioned above, there are a few other serious complications that can arise as a result of Crohn's disease.

Stricture

This is a type of acute bowel obstruction (ABO). This type of obstruction is the most common surgical emergency⁹ for those with IBD.

Gastrointestinal bleeding

Although rare in Crohn's patients, acute lower gastrointestinal bleeding has been known to occur.¹⁰ When it does, it's a potentially life-threatening complication.

Sepsis

One study showed that Crohn's patients are 10-30% more likely to develop abdominal sepsis.¹¹ This extreme reaction to infection can also be life-threatening if not treated.

Treatment

People respond differently to the options available for treating Crohn's disease. There are a variety of medications that your doctor can try to alleviate the symptoms of the disease.

When symptoms get severe, your doctor may recommend bowel rest. During this period, you'll consume only liquids to take pressure off of your intestines and give them time to heal.

Often, surgery is required to treat complications of Crohn's disease, such as gastrointestinal bleeding or obstruction.

The link between them

The connection between Crohn's disease and Hashimoto's disease is still a topic of debate. While having another autoimmune disorder is a risk factor for Hashimoto's, there are conflicting opinions as to whether Crohn's qualifies as an autoimmune disorder.¹²

While often confused for one, Crohn’s doesn’t seem to fit all the criteria.

There have been several studies conducted to investigate the relationship between inflammatory bowel diseases, such as Crohn's, and thyroid disorders, such as Hashimoto's. The results have been mixed.

A literature review¹³ of the studies that have been conducted as of 2016 showed how inconclusive the results are. While some showed a higher prevalence of thyroid disorders in IBD patients, others showed lower prevalence or no prevalence at all. A conclusive answer would require the understanding of which factors are driving those disparities.

There may be similar triggers for the two diseases. For example, bacteria in the gut plays a role in regulating the immune system. Imbalances in these bacteria have been linked to both Hashimoto's thyroiditis¹⁴ and Crohn's disease.¹⁵

Similarly, an increase in intestinal permeability is also associated¹⁶ both with the development of autoimmune diseases and with Crohn's disease. While Hashimoto's disease wasn't among the studied autoimmune diseases, type 1 diabetes, a risk factor⁴ for Hashimoto's, was.

Both diseases are also impacted by smoking. Those who smoke are significantly more likely¹⁷ to develop Crohn’s disease than those who don't.

While smoking makes hypothyroidism in Hashimoto's patients more likely to occur,¹⁸ it appears to decrease the chances of getting the disease itself. However, those who quit smoking see an increase in the risk of developing Hashimoto's during the first two years.

The lowdown

The immune system plays a role in both Hashimoto's and Crohn's disease. Although there are some similar triggers for the two diseases, and they have a few symptoms in common, science isn't conclusive on whether there is a link between the two.

As smoking can worsen both conditions, it's important to quit smoking if you're diagnosed with either of them.

Because Hashimoto's is associated with elevated iodine intake and Crohn's with diets high in fat, your doctor will likely recommend a change in eating habits should you be diagnosed with one or both.

If you experience symptoms of either disease, you should consult with your doctor as soon as possible to minimize the risk of serious complications.