28/11/2023
Autoimmune thyroid disease (AITD) is one of the most common comorbid conditions in rheumatoid arthritis (RA) [1]. Autoimmune thyroid disease encompasses conditions like Hashimoto's thyroiditis (leading to hypothyroidism) and Graves' disease (leading to hyperthyroidism). Both rheumatoid arthritis and AITD are autoimmune conditions, where the immune system mistakenly attacks the body's own tissues. The co-occurrence of RA and AITD can complicate diagnosis and treatment. Symptoms of thyroid dysfunction can sometimes mimic or exacerbate RA symptoms, making accurate diagnosis difficult.
Additionally, thyroid function can affect the metabolism and efficacy of drugs used to treat RA. Due to the high comorbidity rate, it's often recommended that RA patients are regularly monitored for thyroid function, especially if they exhibit symptoms indicative of thyroid dysfunction. Early detection and management of AITD can significantly improve the quality of life for patients with RA.
In a large nationwide cohort study [2] of patients with rheumatoid arthritis, the risk of autoimmune thyroid disease was found to decrease over time following an RA diagnosis, compared to the general population. This decrease was particularly pronounced in patients treated with biologic disease-modifying antirheumatic drugs (bDMARDs), especially TNF inhibitors. No significant differences were noted based on s*x or RA seropositivity.
The study extends previous findings showing a gradual decrease in AITD incidence after initial RA diagnosis. It's the first to investigate how early RA treatment affects the risk of new-onset AITD. The findings align with smaller studies that reported decreased thyroid autoantibodies and altered thyroid function following bDMARD therapy, although some studies have reported mixed results.
The decreased risk of AITD in RA patients following bDMARD treatment supports the hypothesis that immunomodulatory treatment might dampen the inflammatory processes leading to overt AITD. This is consistent with shared genetic and environmental risk factors between RA and AITD. The study observed a more pronounced AITD risk decrease with TNF inhibitors compared to other bDMARDs, possibly due to the larger number of treatments with TNF inhibitors and their earlier use in treatment.
The study also considered other potential factors for the decreased AITD risk and performed robustness tests using different timescales, which did not significantly alter the results. Limitations include the lack of information on thyroid autoantibodies and hormone levels, and potential confounding factors like smoking or obesity.
Overall, the study, with its large size and long follow-up period, provides substantial evidence for the decreased risk of AITD in RA patients following bDMARD treatment, particularly with TNF inhibitors, contributing important insights into the management of RA and associated autoimmune conditions.
References:
1. Raterman, H., et al., Rheumatoid arthritis is associated with a high prevalence of hypothyroidism that amplifies its cardiovascular risk. Annals of the rheumatic diseases, 2008. 67(2): p. 229-232.
2. Waldenlind, K., et al., Disease-modifying antirheumatic drugs and risk of thyroxine-treated autoimmune thyroid disease in patients with rheumatoid arthritis. Journal of Internal Medicine, (00): p. 1-9.