Link Between Hashimoto's Thyroiditis and Systemic Lupus Erythematosus (SLE)
Yes, there is a significant link between Hashimoto's thyroiditis and SLE, with patients having Hashimoto's thyroiditis showing a 90-fold higher prevalence of SLE compared to the general population. 1
Epidemiological Association
- According to clinical practice guidelines, approximately 2.8-3% of patients with autoimmune hepatitis (AIH) are accompanied by SLE 2
- Conversely, 2.7-4.7% of patients with SLE are accompanied by AIH 2
- The prevalence of Hashimoto's thyroiditis in SLE patients is 12.6% compared to 5.6% in controls, representing a 2.4-fold increased risk 3
- Hashimoto's thyroiditis is the most common concurrent autoimmune condition associated with other autoimmune diseases 4
Clinical Implications
- SLE patients with underlying Hashimoto's thyroiditis and hypothyroidism respond more slowly to standard SLE therapy unless the hypothyroidism is adequately treated 5
- Patients with AIH accompanied by SLE had higher IgG levels, and those with higher IgG had a poorer prognosis 2
- SLE patients with Hashimoto's thyroiditis show:
- Less malar rash (p=0.02)
- More anti-Sm antibodies (p=0.04) 3
- The presence of anti-Sm antibodies favors the association between SLE and Hashimoto's thyroiditis 3
Screening Recommendations
- Due to the significant overlap between these autoimmune conditions, patients with one autoimmune disease should be screened for others:
- SLE patients should be screened for thyroid dysfunction with TSH, Free T4, and thyroid autoantibodies (TPO and TgAb)
- Hashimoto's thyroiditis patients should be monitored for symptoms of SLE
Monitoring Considerations
- In patients with both conditions:
- Regular monitoring of thyroid function is essential 4
- For patients with Hashimoto's on appropriate replacement therapy, evaluate clinical and biochemical response every 6-12 months 4
- Monitor for liver enzyme abnormalities, as 19.4% of SLE patients with high liver enzyme levels are associated with AIH 2
Pathophysiological Connection
- Both conditions share common immunological pathways involving autoantibody production and T-cell dysregulation
- The presence of multiple positive autoantibodies (both thyroid and SLE-specific) indicates a broader autoimmune dysregulation 3
- Studies show that treatments targeting immune regulation can benefit both conditions simultaneously 6
Clinical Pitfalls to Avoid
- Don't attribute all symptoms to a single autoimmune disease when multiple may be present
- Don't overlook thyroid dysfunction in SLE patients with poor response to standard therapy
- Remember that disease activity and cumulative damage in SLE are not directly related to the presence of Hashimoto's thyroiditis 3
- Be vigilant for the development of additional autoimmune conditions in patients already diagnosed with either SLE or Hashimoto's thyroiditis 7