Increased risk venous thromboembolism among patients with hyperthyroidism: a systematic review and meta-analysis of cohort studies

Background: Studies have suggested that patients with hyperthyroidism may have a higher risk of venous thromboembolism (VTE) compared to individuals with normal thyroid function, although the data is quite limited. This systematic review and meta-analysis aims to comprehensively investigate this risk by summarizing all available studies. Methods: A systematic review was performed using the MEDLINE and Embase databases from inception to February 2019 to identify all cohort studies that compared the risk of incident VTE in patients with hyperthyroidism versus individuals without hyperthyroidism. Pooled risk ratio and 95% confidence interval were calculated using random-effect, generic inverse-variance method. Results: A total of 5 retrospective cohort studies with 237,667 cases with hyperthyroidism and 4,615,907 comparators without hyperthyroidism were included. The pooled analysis found a significantly increased risk of incident VTE among patients with hyperthyroidism, with a pooled risk ratio of 1.332 (95% CI, 1.275-1.391; I-2 14%). The funnel plot was asymmetric and may suggest the presence of publication bias in favor of studies that showed positive association. Conclusion: A significantly increased risk of incident VTE among patients with hyperthyroidism compared to individuals without hyperthyroidism was demonstrated in this meta-analysis.