People with multiple sclerosis (MS) may have a higher risk of developing thyroid conditions. However, researchers are yet to uncover the exact link between them.

MS is a chronic autoimmune condition that involves the immune system attacking the healthy cells of the central nervous system. This damage can cause different symptoms among different people.

The two most common thyroid conditions are hypothyroidism and hyperthyroidism. Hypothyroidism occurs when the thyroid does not produce enough thyroid hormone for the body. Hyperthyroidism occurs when the thyroid produces too much thyroid hormone.

The most common cause of hypothyroidism is an autoimmune condition called Hashimoto’s disease. Graves’ disease is also an autoimmune condition and is the most common cause of hyperthyroidism.

Although these are separate conditions, they may share a link that makes it more likely a person will develop a thyroid condition if they have MS.

The following sections explain what scientists currently know about this possible connection.

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MS and autoimmune hypothyroidism frequently occur together. However, other autoimmune conditions, including type 1 diabetes, rheumatoid arthritis, and psoriasis, may occur more frequently than hypothyroidism with MS.

The links between MS and thyroid disorders are unclear, but studies indicate that having one condition may make developing the other more likely.

A 2005 study found that MS shares similar development pathways with diseases that cause thyroid dysfunction, primarily Graves’ and Hashimoto’s. Hashimoto’s disease is the most common cause of hypothyroidism, while Graves’ disease is the most common cause of hyperthyroidism.

In a 2018 study, researchers further explored the connections between MS and Hashimoto’s disease. They found that both conditions share a common deregulation of anti-inflammatory mechanisms in the body. In other words, both conditions involve similar inflammation mechanisms.

However, the study also noted that additional research is necessary to fully understand the relationship between MS and Hashimoto’s disease.

MS treatments and thyroid disorders

Certain treatments for MS may trigger thyroid issues.

A 2020 review found that relapse-remitting MS patients undergoing treatment with interferon beta-1b medications had a higher rate of thyroiditis than those taking other medications. A small 2021 study supported the theory, finding a significant increase in thyroid disorder markers in MS patients 1 year after interferon beta treatment.

In a 2017 study involving 69 people with MS receiving treatment with alemtuzumab infusions, 20% developed thyroid disease within 18 months of their initial treatment. Of those who developed thyroid disease, 50% developed hyperthyroidism.

However, the researchers also found that thyroid disease spontaneously resolved or remained subclinical in roughly one-third of the participants.

As a result, the study authors recommended ongoing active monitoring of people receiving treatment with alemtuzumab infusions for the first 5 years.

If anyone has concerns about the impact of MS treatment on their thyroid or any other potential side effects, they should talk with a doctor to learn more about other treatment options.

Thyroid disorders can produce symptoms similar to MS. The type of thyroid disorder a person has can alter symptom presentation.

Hypothyroidism and MS

Hypothyroidism develops when the thyroid does not produce enough thyroid hormone for the body.

The thyroid hormone is crucial to several organs and tissues throughout the body. If these organs do not receive enough hormone, they will not perform as well as they should.

Hypothyroidism causes some symptoms that are similar to those of MS, including:

  • joint and muscle pain
  • difficulty handling cold temperatures
  • fatigue
  • depression
  • a slowed heart rate
  • constipation
  • weight gain
  • fertility issues

The National Multiple Sclerosis Society (NMSS) states that some symptoms of MS that are similar to those of hypothyroidism include:

  • depression
  • fatigue
  • constipation or other bowel issues
  • muscle weakness
  • sexual issues

Although some research has suggested a possible link, having one condition does not mean a person will typically get the other.

Hyperthyroidism and MS

Hyperthyroidism can cause serious problems with the heart, bones, muscles, menstrual cycle, and fertility. It can also affect the skin and eyes.

Symptoms of hyperthyroidism include:

  • irregular heartbeat
  • frequent bowel movements or diarrhea
  • an enlarged thyroid or goiter
  • heat intolerance
  • nervousness or irritability
  • fatigue
  • muscle weakness
  • trembling hands
  • difficulty sleeping
  • weight loss

According to the NMSS, fatigue, muscle weakness, bowel issues, and tremors are also symptoms of MS.

MS and thyroid conditions may also share common risk factors.

Some research suggests the cause of MS is likely a combination of genetic predisposition and infections that trigger an immune response.

Shared risk factors include smoking, obesity, and low exposure to the sun. However, these factors are not useful for predicting a person’s likelihood of developing MS.

There are several risk factors for hypothyroidism, including:

  • family history
  • recent radiation treatment
  • having type 1 diabetes or rheumatoid arthritis

A person’s risk of developing Graves’ disease increases if other family members have the condition. Hyperthyroidism may develop from a combination of genes and an outside trigger, such as a virus.

Some research has also shown that shared risk factors between MS and thyroid issues include genetic susceptibility and environmental exposure. In other words, a person with certain genetic susceptibility or environmental exposure may be at increased risk of developing both MS and a thyroid condition.

However, the researchers stated that more investigations are necessary to fully understand the risk factors.

For more information and research about MS, visit our dedicated hub.

Below are some frequently asked questions regarding MS and thyroid conditions.

Can thyroid issues mimic MS?

Hyperthyroidism and hypothyroidism both share symptoms with MS, such as fatigue and muscle pains. However, doctors can distinguish the conditions with diagnostic tests.

Are Hashimoto’s and MS related?

Research suggests that Hashimoto’s disease and MS cause similar impairment to the body’s anti-inflammatory processes. People with MS may develop Hashimoto’s, but the two remain distinct diseases.

Can hypothyroidism cause demyelination?

Hypothyroidism does not cause demyelination. However, chronic hypothyroidism can cause peripheral neuropathy or nerve damage in rare cases.

MS and thyroid conditions share some similar potential causes and symptoms. However, they are not directly related.

People with MS, or either hypothyroidism or hyperthyroidism, may or may not develop the other condition.

A person with MS should talk with a doctor about screening for thyroid issues. They may develop thyroid issues due to having similar risk factors or using certain MS medications.