Interference between rheumatoid arthritis and autoimmune thyroid diseases: A bidirectional Mendelian randomization

Area of Science:

• Rheumatology
• Endocrinology
• Genetic Epidemiology

Background:

• The etiological link between rheumatoid arthritis (RA) and autoimmune thyroid disease (AITD) is not fully understood.
• Previous studies have yielded conflicting results regarding the association between RA and AITD.
• Genetic factors may play a role in the co-occurrence of these autoimmune conditions.

Purpose of the Study:

• To investigate the potential causal relationship between rheumatoid arthritis and autoimmune thyroid disease using a bidirectional Mendelian randomization approach.
• To assess whether RA increases the risk of AITD (specifically autoimmune thyroiditis and Graves' disease) and vice versa.

Main Methods:

• Bidirectional Mendelian randomization (MR) analysis was employed.
• Single nucleotide polymorphisms (SNPs) associated with RA, autoimmune thyroiditis (AIT), and Graves' disease (GD) were obtained from the FinnGen database.
• Inverse variance weighted (IVW) method was used for primary analysis, with MR-Egger, Cochran Q, and sensitivity analyses to assess pleiotropy and heterogeneity.

Main Results:

• Rheumatoid arthritis was significantly associated with an increased risk of AIT (OR 1.552) and GD (OR 1.177).
• Graves' disease showed a significant association with an increased risk of RA (OR 1.030), while AIT did not show a significant association with RA risk (OR 0.994).
• MR analyses confirmed robustness, with no significant horizontal pleiotropy or heterogeneity detected.

Conclusions:

• Rheumatoid arthritis may be a risk factor for developing autoimmune thyroid disease, particularly Graves' disease.
• Graves' disease may also increase the risk of developing rheumatoid arthritis.
• Proactive screening for AITD in RA patients and for RA in GD patients is recommended to improve patient outcomes.