Periodontal disease in patients with thyroid disorders: a systematic review and meta-analysis

Thyroid disorders, particularly primary hypothyroidism, have been linked to periodontal disease through impaired bone remodeling and inflammation, but earlier meta-analyses did not rate the certainty of the evidence. PubMed, Embase, and the Cochrane Central Register of Controlled Trials were searched up to 19 June 2026 for studies comparing periodontal outcomes between adults with thyroid disorders and systemically healthy controls. Random effects meta-analysis was restricted to primary hypothyroidism, and other thyroid disorders were synthesized descriptively. Risk of bias and certainty of evidence were assessed with a tool for non randomized studies of exposures and the Grading of Recommendations Assessment, Development and Evaluation approach. Of 1,588 records screened, seven studies were included and five (598 cases and 533 controls) were meta-analyzed. Patients with hypothyroidism had a higher prevalence of periodontitis (risk ratio 1.92, 95% confidence interval 1.11 to 3.33), deeper probing pockets (mean difference 0.86 mm, 0.22 to 1.50), and greater clinical attachment loss (1.80 mm, 0.33 to 3.28). Bleeding on probing and plaque index did not differ. Heterogeneity was high (I² 94% to 98%), and significant findings were not robust to omission of single studies or to a small sample adjustment. Certainty of evidence was low for probing depth and attachment loss and very low for the other outcomes. Two descriptive studies (hyperthyroidism and mixed dysfunction), both at high risk of bias, reported worse periodontal status. Primary hypothyroidism may be associated with worse periodontal status, but the evidence is uncertain and hypothesis generating. PROSPERO registration: CRD420261428495, registered 19 June 2026.