Objectives Hypothyroidism and inflammatory arthritis tend to coexist, but data on this association are sparse. In terms of cardiovascular risk, this association may have clinical relevance as this coexistence may carry an additional cardiovascular risk. This study calculates, first, the prevalence of hypothyroidism in patients with inflammatory arthritis and, second, the cardiovascular disease (CVD) prevalence rate in patients with either hypothyroidism or inflammatory arthritis, or both.

Methods Data from the Netherlands Information Network of General Practice, a representative Dutch sample of 360 000 registered patients, were used. Prevalence rates of hypothyroidism were calculated, and multilevel logistic regression analyses were used to calculate CVD prevalence rates.

Results Hypothyroidism prevalence was 6.5% in female patients with arthritis compared to 3.9% in controls (p<0.001). CVD prevalence was 4.3% in patients with hypothyroidism, 5.9% in patients with inflammatory arthritis, 14.3% in patients with hypothyroid inflammatory arthritis and 2.1% in controls. Adjusted CVD prevalence rates were 1.2 (95% CI 0.99 to 1.4) for hypothyroidism, 1.5 (95% CI 1.1 to 2.0) for inflammatory arthritis and 3.7 (95% CI 1.7 to 8.0) for hypothyroid inflammatory arthritis as compared with controls.

Conclusions These data raise awareness on the coexistence of hypothyroidism and inflammatory arthritis and emphasise the importance of cardiovascular risk management in these patients, particularly when hypothyroidism and inflammatory arthritis coexist.