Causal relationship between rheumatoid arthritis and hypothyroidism or hyperthyroidism: a bidirectional two-sample...

Area of Science:

• Endocrinology and Immunology
• Genetic Epidemiology

Background:

• The relationship between Rheumatoid arthritis (RA) and thyroid dysfunction (hypothyroidism/hyperthyroidism) is complex and debated.
• Conventional observational studies face limitations like confounding factors and reverse causality, hindering definitive causal inference.

Purpose of the Study:

• To investigate the potential causal relationship between Rheumatoid arthritis (RA) and hypothyroidism/hyperthyroidism.
• To utilize Mendelian randomization (MR) to overcome limitations of observational research.

Main Methods:

• Conducted a bidirectional two-sample univariable Mendelian randomization (MR) analysis.
• Performed multivariate MR analyses, adjusting for body mass index (BMI), smoking, and alcohol intake.

Main Results:

• Rheumatoid arthritis (RA) showed a causal effect on hypothyroidism (OR=1.07) and hyperthyroidism (OR=1.32).
• Hypothyroidism demonstrated a causal influence on RA (OR=1.21), while hyperthyroidism did not (OR=0.91).
• These causal associations remained robust after multivariate adjustments.

Conclusions:

• Mendelian randomization analyses confirm a causal link between RA and thyroid dysfunction.
• Hypothyroidism is causally associated with RA, whereas hyperthyroidism is not.
• Findings clarify the etiological relationship between RA and thyroid disorders.