A Comparison of Chronic Fatigue, Fibromyalgia, and Thyroid Disease

Interesting Overlap in Certain Symptoms, Like Fatigue and Pain

fatigue, chronic fatigue syndrome, fibromyalgia, hashimoto's

People with Hashimoto's autoimmune thyroid disease often experience significant fatigue and body aches. While these symptoms are common in Hashimoto's, they can also be markers of other diseases, like chronic fatigue syndrome or fibromyalgia. 

Let's take a closer look at these three disorders, including how their symptoms overlap, and even how their underlying cause may be related.


Chronic Fatigue Syndrome

The primary symptom of chronic fatigue syndrome is unrelenting exhaustion—so much so that even the smallest physical exertion can put a person in bed for days (which is why this syndrome is also called systemic exertion intolerance disease).

Other symptoms of chronic fatigue syndrome include thinking and memory problems, sleep difficulties, joint aches, and sore lymph nodes, especially in the neck and underarm area.


While fatigue often occurs in fibromyalgia, the primary complaint is a generalized musculoskeletal pain. Other symptoms include cognitive disturbances, depression and/or anxiety, headaches, and paresthesias. 


With Hashimoto's, the thyroid fails to produce sufficient thyroid hormone to regulate metabolism.

Symptoms of an underactive thyroid usually include fatigue and muscle and joint pain, as well as one or more other symptoms like:

  • Excessive weight gain
  • Hair thinning or loss
  • Dry and coarse skin
  • Constipation
  • Swelling and fluid retention
  • Depressed mood
  • Menstrual irregularities


Chronic Fatigue Syndrome

For chronic fatigue syndrome, there is no official blood or imaging test to make a firm diagnosis. Instead, doctors typically rule out other underlying illnesses before making a chronic fatigue syndrome diagnosis. In other words, it's a diagnosis of exclusion, when other "testable" conditions, like thyroid disease or infection, have been ruled out. 


The diagnosis of fibromyalgia requires a thorough "tender point" examination, which entails pressing on specific muscles, like the upper outer part of the buttock. Like with chronic fatigue syndrome, other medical conditions, like thyroid disease or inflammatory muscle disease, need to be ruled out first. 


Unlike chronic fatigue syndrome and fibromyalgia, the diagnosis of Hashimoto's tends to be more straightforward. This is because sensitive blood tests, like the thyroid function panel and thyroid antibodies, can be used.  

Even so, despite the fact that concrete medical tests exist to diagnose thyroid problems, misdiagnosis still occurs. For instance, Hashimoto's may be misdiagnosed as depression, stress, or "female" hormonal problems such as premenstrual syndrome, post-partum depression, or menopause symptoms.

These same misdiagnoses can be applied to those who really have chronic fatigue syndrome or fibromyalgia.

Another oversight that may occur is when a person has more than one condition going on. For example, it's not uncommon for chronic fatigue syndrome and fibromyalgia to co-occur. In fact, according to an older study, approximately 70 percent of people with fibromyalgia meet the criteria for chronic fatigue syndrome.

It's also possible for fibromyalgia and Hashimoto's to co-occur. In this example, since muscle aches may be a component of Hashimoto's, it's reasonable to treat a person's underactive thyroid, and then see if their pain improves. If other thyroid symptoms improve, but the aches remain, then an alternative diagnosis to those aches (like fibromyalgia) needs to be considered.  


Until definitive research is completed on chronic fatigue syndrome, fibromyalgia, and Hashimoto's, there are many hypotheses as to the cause of these diseases.

Some medical researchers believe that a virus (such as the Epstein-Barr virus) is at the core of these diseases, especially chronic fatigue syndrome.

Other researchers believe bacterial infection, stress, an accident (such as an auto accident), or other trauma may chronically activate the immune system. The immune system, which ordinarily returns to normal after successfully fighting an infection, then remains in a hyperactive state.

Others have suggested the development of one autoimmune disorder, such as rheumatoid arthritis or lupus, may then precipitate the onset of chronic fatigue syndrome, fibromyalgia, or Hashimoto's. Still, other experts believe that a hormonal issue, like a low cortisol level, may play a role, especially in the development of chronic fatigue syndrome.

Finally, certain experts are looking for autoimmune thyroid disease itself as perhaps the underlying cause of some chronic fatigue syndrome and fibromyalgia symptoms, or perhaps the root cause of the diseases themselves.

A Word From Verywell

If you are concerned you have chronic fatigue syndrome, fibromyalgia, or Hashimoto's (or more than one), please see a doctor for a proper evaluation and diagnosis.

Moreover, if you are diagnosed with one of these conditions and continue to have bothersome symptoms, like fatigue or pain, be sure to re-visit this with your doctor.

In the end, remain resilient in your healthcare and try to be patient too. Often times a person's "health" story has to unfold over more than one doctor visit.

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Article Sources
  • Gluckman SJ. (2017). Clinical features and diagnosis of chronic fatigue syndrome (systemic exertion intolerance disease). Aronson MD, ed. UpToDate. Waltham, MA: UpToDate Inc. 
  • Goldenberg DL. (2017). Clinical manifestations and diagnosis of fibromyalgia in adults. Schur PH, ed. UpToDate. Waltham, MA: UpToDate Inc. 
  • Hailioglu S, Ekinci B, Uzkeser H, Sevimli H, Carlioglu A, Macit PM. Fibromyalgia in patients with thyroid autoimmunity: prevalence and relationship with disease activity. Clin Rheumatol. 2017 Jul;36(7):1617-21.