The mediating role of serum 25-hydroxyvitamin D on the association between reduced sensitivity to thyroid hormones and periodontitis in Chinese euthyroid adults.

Abstract

Thyroid dysfunction is closely associated with periodontitis. We aim to explore the association between sensitivity to thyroid hormones (THs) and periodontitis and to investigate the mediating role of serum 25-hydroxyvitamin D[25(OH)D] in this relationship in Chinese euthyroid populations. This population-based retrospective study included 2,530 euthyroid participants. Central sensitivity to THs was assessed by the thyroid feedback quantile-based index (TFQI), parametric thyroid feedback quantile-based index (PTFQI), thyrotrophic thyroxine resistance index (TT4RI) and thyroid-stimulating hormone index (TSHI), while FT3/FT4 was evaluated to assess peripheral sensitivity. Multivariable regression analysis and restricted cubic spline were performed to explore the association between sensitivity to THs and periodontitis. Threshold effect and subgroup analysis were also conducted. Mediation analysis was performed to estimate direct and indirect effects through 25(OH)D. Multivariable regression analysis indicated that central sensitivity to THs indices(per SD increase) were positively associated with periodontitis risk [TFQI: OR=1.19,95% CI (1.09, 1.31); PTFQI: OR=1.22, 95% CI(1.12,1.34); TSHI: OR=1.36, 95% CI (1.21,1.52); TT4RI: OR=1.43, 95% CI (1.25,1.63)](all P value<0.001). TT4RI only had a non-linear relationship with periodontitis in euthyroid participants. Subgroup analysis showed that no significant correlations were founded among those aged over 65 years or with hypertension/diabetes. Mediation analysis revealed that the proportions mediated by 25(OH)D on the association of TFQI, PTFQI,TSHI, TT4RI and periodontitis risk were 16.37%, 16.43%, 9.93% and 10.21%, respectively. Impaired central sensitivity to THs is positively associated with periodontitis in euthyroid and serum 25(OH)D might be one of its biological mechanisms.