The Connection Between Fibromyalgia and Thyroid Disease

Thyroid disease, especially hypothyroidism, and fibromyalgia share many symptoms. In fact, having one of these conditions may predispose you to the other, and having both impacts each disease. Despite the associations, theories about the cause of these related conditions are not concrete. Researchers have proposed autoimmunity, dysfunction of the hypothalamus, and more possibilities.

Who They Affect

Thyroid disease and fibromyalgia are each very common in the United States.

• Estimates suggest that at least 5 percent of adults in the United States are living with hypothyroidism. Hashimoto's disease, a type of autoimmune hypothyroidism, is the most common form.
• According to the Centers for Disease Control and Prevention (CDC), 2 percent of the population, or around 4 million people, are living with fibromyalgia.

These numbers do not include others who may be undiagnosed.

Combined Occurrence

Not only are hypothyroidism and fibromyalgia both common, but they frequently occur together. According to one study, the prevalence of fibromyalgia in the general population was 2 percent to 7 percent, but as high as 30 percent to 40 percent in people with hypothyroidism. Using newer diagnostic criteria for fibromyalgia, the incidence may be even higher.

Among people with hypothyroidism, fibromyalgia was more common in those who were overweight, had positive anti-thyroperoxidase antibodies, and who had been living with thyroid disease for a long period of time.

Similarities in Epidemiology

Thyroid disease and fibromyalgia tend to affect a similar population of people:

• Sex: Both conditions are much more common in women.
• Age: Both conditions begin most commonly during the childbearing years and in middle age, though they can occur at any age.

Similarities such as these have played into some hypotheses about potential causes.

Potential Causes

Hashimoto's disease is an autoimmune disease in which autoantibodies (antibodies against one's self) damage thyroid tissue. There is a great deal of controversy about the underlying cause of fibromyalgia.

Some have postulated that both autoimmune thyroid disease and fibromyalgia are caused by a similar underlying process that can predispose a person to both conditions, but neither this nor any other theory has been confirmed.

Some of the possibilities that have been suggested include:

Autoimmunity

Theories vary, though some have postulated that underlying autoimmune disease precipitates the development of both conditions.

The autoimmune basis of Hashimoto's disease is supported by the presence of anti-thyroperoxidase (TPO) antibodies. These antibodies are found in nearly all people with Hashimoto's thyroid disease and in some healthy people, too, particularly in women.

One study found a potential link to autoimmune disease with fibromyalgia as well. Compared to the control subjects, people with fibromyalgia had a high degree of positivity to a related thyroid antibody. The authors of the study also cited numerous other studies that show a higher prevalence of thyroid antibodies in people with fibromyalgia compared to the general population.

Suppression of the Hypothalamus

The hypothalamus is a region of the brain that has been likened to the utility center. It functions to maintain homeostasis, a steady state in the body, by regulating hormone levels (including thyroid hormones), sleep, temperature, hunger, and the autonomic nervous system (the involuntary part of the nervous system that controls blood pressure, blood flow, digestion, and much more).

Suppression of the hypothalamus may occur due to problems with the mitochondria in hypothalamic cells, the organelles that are considered the "energy furnaces" of cells.

Some researchers have suggested that such dysfunction of the hypothalamus may be the root cause of both disorders and that, by itself, hypothalamic dysfunction can cause many of the symptoms attributed to thyroid disease and fibromyalgia.

Trauma

As with some infections, both autoimmune thyroid disease and fibromyalgia are sometimes preceded by trauma. Trauma activates the immune system. This activation might lead to a hyperactive immune state (causing autoimmunity) after the injury has resolved.

Hormonal Problems and Physical Stress on the Body

Other hormonal problems or conditions that stress the body, such as infections, have been associated with both fibromyalgia and thyroid disease.

Shared Symptoms

There are a number of similar hypothyroidism and fibromyalgia symptoms, as well as some that are more common with one condition than the other.

Symptoms that are very common among people with either hypothyroidism or fibromyalgia include:

• Fatigue, exhaustion, and non-restful sleep
• Body aches (muscle and joint pain)
• Cognitive problems, often referred to as "brain fog"
• Depression and anxiety

Autoimmune thyroid disease often leads to worsening fibromyalgia symptoms. Fibromyalgia may also worsen the symptoms of thyroid disease, or make it more difficult to know if thyroid hormone replacement therapy is optimal.

Diagnosis

Hypothyroidism and fibromyalgia can both be misdiagnosed.

Hypothyroidism

The diagnosis of hypothyroidism often begins with a TSH test, though some experts believe that a normal TSH is insufficient to rule out thyroid disease, especially in those who have a family history of an autoimmune thyroid condition (such as Hashimoto's thyroiditis or Graves' disease).

Additional diagnostic tests may be ordered to paint a fuller picture of your thyroid health, including free T4, total and free T3, and thyroid antibody tests.

Fibromyalgia

The diagnosis of fibromyalgia is primarily a clinical diagnosis based on symptoms of pain, fatigue, and cognitive problems. Since undertreated hypothyroidism can cause symptoms that are very similar, it can be challenging to know whether a person meets the criteria for fibromyalgia with hypothyroidism.

During an evaluation for possible fibromyalgia, thyroid function testing is usually done. If autoimmune hypothyroidism is found, it's reasonable to treat only the thyroid condition at first and see if the pain resolves. If a person is already on thyroid replacement therapy and has symptoms of fibromyalgia, the goal should be optimal control before a diagnosis is made.

Even if you have had normal thyroid tests in the past, if your fibromyalgia symptoms are worsening or not responding to treatment, your healthcare provider may repeat your thyroid tests.

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Differential Diagnoses

To further complicate matters, other conditions may cause symptoms that are similar to fibromyalgia and hypothyroidism. These other possible diagnoses can make the two conditions less obvious and challenging to identify, perhaps even masking the development of fibromyalgia with hypothyroidism and vice versa.

Other diagnoses that may also be considered include:

• Anemia
• Depression and/or anxiety
• Vitamin D deficiency
• Kidney disease
• Liver disease
• Infections (such as mononucleosis, Lyme disease, and more)
• Sleep apnea
• Hormonal conditions
• Other autoimmune diseases (such as lupus)

Living With These Conditions

In addition to taking any recommended medication, there are things you can do that can help you live your best life with both conditions.

Exercise

While the fatigue associated with both thyroid disease and fibromyalgia can hamper your desire to exercise, there are many benefits to moving.

• Exercising when you have thyroid disease can increase energy levels, improve mood, and bump metabolism in those struggling with weight gain.
• As a caveat, exercise with fibromyalgia can be a bit more tricky. While moderate exercise is often beneficial, some people experience a significant worsening of fibromyalgia-related fatigue after exercise that has been coined post-exertional malaise.

Since everyone is different, it's important to know your own body. Keeping a daily journal of exercise habits and energy levels may help you determine the appropriate amount of activity that is helpful for you.

Reduce Stress

Stress management is important for anyone, but it's particularly important for people with these two conditions. Not only do both thyroid disease and fibromyalgia add to everyday stress levels, but increased stress can exacerbate their symptoms.

Since some stressors can't be eliminated, researchers are beginning to look at ways that people can develop emotional resilience, which is the ability to cope with adversity in life. There are now a number of integrative medical centers that offer resilience training for people coping with chronic medical conditions.

Get Better Sleep

Both conditions commonly cause sleep problems such as insomnia and night sweats, and sleep problems exacerbate the other symptoms of thyroid disease and fibromyalgia.

Given the importance of sleep with regard to these symptoms, it's worth taking a good inventory of your sleep habits and making changes to set yourself up for a good night's rest. If you continue to have concerns, talking to your healthcare provider or seeing a sleep specialist may be helpful.

Improve Your Diet

A healthy diet is wise for anyone, but some foods that are usually considered healthy may have anti-thyroid effects.

A Word From Verywell

Thyroid disease and fibromyalgia have many commonalities, though the exact connection between the two conditions is still unclear. It's important to be aware of both conditions and potential interactions when talking to your healthcare providers about your symptoms and treatment options.