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TOPLINE: 

Patients with autoimmune thyroid disease had a 65% higher risk of developing microscopic colitis, with the strongest association observed in patients diagnosed with microscopic colitis before 50 years of age. 

METHODOLOGY:

• Researchers conducted this nationwide case-control study to examine the association between autoimmune thyroid diseases and microscopic colitis.
• They included 10,301 patients (median age, 63.8 years; 71.7% women) with biopsy-confirmed microscopic colitis diagnosed between 2006 and 2017 and matched them with 48,712 control individuals from the general population who did not have microscopic colitis.
• A sibling comparison study was conducted in 5810 patients (median age, 59.3 years; 71.7% women) with microscopic colitis and 11,210 of their siblings without the condition to minimise confounding related to shared genetics and environment.
• Data on preexisting autoimmune thyroid diseases, specifically Hashimoto's thyroiditis or Graves' disease, were retrieved from Swedish national healthcare registers.

TAKEAWAY:

• Preexisting autoimmune thyroid disease was more common in patients with microscopic colitis than in control individuals, yielding an odds ratio (OR) of 1.65 (95% CI, 1.54-1.77) after adjusting for covariates.
• The association between preexisting autoimmune thyroid disease and microscopic colitis remained significant even when siblings of patients were used as comparators (adjusted OR [aOR],1.26; 95% CI, 1.11-1.43).
• Patients diagnosed with microscopic colitis before 50 years of age showed the strongest association with preexisting autoimmune thyroid diseases (aOR, 2.41; 95% CI, 2.02-2.89).
• No significant differences were found between the subtypes of microscopic colitis (collagenous colitis and lymphocytic colitis) or between sexes.

IN PRACTICE:

"Our findings hold clinical relevance for both endocrinologists and general practitioners caring for patients with AITDs [autoimmune thyroid diseases]. Patients with persistent gastrointestinal symptoms despite achieving euthyroidism should be evaluated for underlying MC [microscopic colitis]," the authors wrote.

SOURCE:

The study was led by David Bergman, MD, PhD, and Xiaoying Kang, PhD, MPH, Karolinska Institutet, Stockholm, Sweden, and was published online on March 5, 2025, in The Journal of Clinical Endocrinology & Metabolism. 

LIMITATIONS:

The study was strictly register-based, leading to a lack of information on potential confounding lifestyle factors such as body mass index and smoking. The national patient register did not include primary care diagnoses, though the impact of this limitation was likely low, as Graves' disease was almost exclusively managed in specialist care. Additionally, residual surveillance bias may have been present due to increased monitoring of patients with autoimmune thyroid diseases.

DISCLOSURES:

This study was supported by the Karolinska Institutet and Stockholm County Council. Some authors reported receiving research funding or support from the Swedish Research Council International Postdoc Grant, the European Crohn's and Colitis Organization, or other sources. One author declared receiving financial support from various pharmaceutical companies and coordinating a study funding by a pharmaceutical company. Another author acted as an advisory board member for a pharmaceutical company.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.