BACKGROUND: Thyroid dysfunction causes various oral manifestations, while periodontal disease is a chronic inflammatory condition affecting the supporting structures of teeth. This systematic review and meta-analysis aimed to evaluate the effects of thyroid dysfunction on periodontal disease indices, synthesizing evidence to clarify the relationship between these conditions. METHODS: A comprehensive search followed PRISMA guidelines across Medline, Scopus, Web of Science, and Google Scholar from inception to September 2024. Studies included adults with diagnosed thyroid dysfunction and healthy controls. Data were extracted on thyroid function tests and periodontal disease indices. The risk of bias and quality of studies were assessed using funnel plots, Begg's and Egger's indices, and the Cochrane tool. Effect sizes were calculated using standard mean difference (SMD) via Comprehensive Meta-Analysis software. RESULTS: Eight studies (seven publications) were included. The analysis revealed that patients with thyroid dysfunction exhibited significantly higher periodontal disease indices than controls, with a pooled SMD of 0.369 (95% CI: 0.194-0.545, p <
0.001). The effects of thyroid dysfunction were found on clinical attachment level and pocket probing depth, but not on other indices like the gingival and plaque indexes. Sensitivity analysis confirmed the robustness of these findings. The quality of studies was low, with notable risks of bias. CONCLUSIONS: Thyroid dysfunction is associated with increased periodontal disease indices, highlighting the need for further research to explore the underlying mechanisms and improve clinical management strategies for affected patients. Future studies should aim for higher methodological rigor to enhance the reliability of findings.