Is fibromyalgia (FM) associated with Hashimoto's thyroiditis?

Association Between Hashimoto's Thyroiditis and Fibromyalgia

Fibromyalgia is strongly associated with Hashimoto's thyroiditis, with studies showing a prevalence of fibromyalgia in 30-62% of Hashimoto's thyroiditis patients compared to only 2-7% in the general population. 1

Evidence for the Association

Prevalence and Risk

• Multiple studies demonstrate a significant association between Hashimoto's thyroiditis and fibromyalgia:
  • A cross-sectional study found fibromyalgia in 62% of Hashimoto's thyroiditis patients 1
  • Another study showed that 31% of Hashimoto's thyroiditis patients had fibromyalgia comorbidity 2
  • Non-specific rheumatic manifestations were found in 20% of Hashimoto's thyroiditis patients compared to only 6.8% in controls 3

Clinical Features and Correlations

• The association appears independent of thyroid function status:

  • 62% of Hashimoto's patients with rheumatic manifestations were euthyroid and only 7% were overtly hypothyroid 3
  • Antithyroid peroxidase antibody (TPOAb) positivity, disease duration, and waist circumference were significantly associated with concomitant fibromyalgia 1

• Patients with thyroid autoimmunity showed higher prevalence of:

  • Polyarthralgias and myalgias 3
  • Dry eyes, burning or pain with urination, allodynia, blurred vision, and sore throat 4

Pathophysiological Considerations

The relationship between Hashimoto's thyroiditis and fibromyalgia appears to be more than coincidental. Evidence suggests that thyroid autoimmunity itself, rather than thyroid dysfunction, may play a role in fibromyalgia pathogenesis:

• Thyroid autoimmunity may represent a predisposition for fibromyalgia development 2
• The presence of thyroid antibodies correlates with fibromyalgia disease severity 4
• Female predominance is more pronounced in patients with both conditions (F:M ratio 24:1 vs 5:1 in Hashimoto's alone) 3

Clinical Implications

Diagnostic Considerations

• Screen for fibromyalgia in Hashimoto's thyroiditis patients presenting with widespread pain, fatigue, or sleep disturbances
• Consider thyroid autoimmunity testing in fibromyalgia patients, particularly those with treatment resistance
• The presence of TPOAb appears to be an independent risk factor for fibromyalgia, regardless of thyroid function 1

Management Approach

• Recognition of the fibromyalgia component in Hashimoto's thyroiditis is crucial for optimal management 1
• Addressing both conditions may improve treatment outcomes
• Monitoring thyroid antibodies may provide insight into fibromyalgia symptom severity

Common Pitfalls to Avoid

• Attributing all symptoms to hypothyroidism without considering fibromyalgia as a comorbidity
• Focusing solely on thyroid hormone replacement without addressing fibromyalgia symptoms
• Overlooking thyroid autoimmunity in euthyroid patients with fibromyalgia symptoms

Based on the available evidence, fibromyalgia (option B) is the condition most strongly associated with Hashimoto's thyroiditis among the given options. The other conditions (osteoarthritis, non-celiac gluten sensitivity, and ADHD) do not have established associations with Hashimoto's thyroiditis in the provided evidence.