Abstract
BACKGROUND: To evaluate the relationship between thyroid function and thyroid homeostasis parameters with the prevalence of chronic kidney disease (CKD) and furtherly explore the all-cause and cardiovascular mortality among individuals with CKD using data from the National Health and Nutrition Examination Survey (NHANES) 2007-2012. METHODS: This study included 8,526 adults, including 1,625 patients with CKD. Thyroid function included serum free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH). The thyroid homeostasis parameters, including FT3/FT4, thyroid feedback quantile-based index (TFQI(FT4), TFQI(FT3)), thyrotrophic thyroxine resistance index (TT4RI, TT3RI) and thyroid-stimulating hormone index (TSHI) were calculated. Weighted multivariate logistic regression models to explore the association between thyroid function and thyroid homeostasis parameters and the prevalence of CKD. Cox proportional hazards models were used to investigate the association of thyroid function and thyroid homeostasis parameters with all-cause and cardiovascular mortality among CKD patients. Kaplan-Meier curves compared survival across the quartiles of the thyroid function and thyroid homeostasis parameters among CKD patients. Furthermore, the restricted cubic splines were used to explore the non‑linear relationships. RESULTS: The weighted multivariate logistic regression models showed that FT4 was positively correlated with the prevalence of CKD, FT3/FT4 and TFQI(FT3) were negatively correlated with mortality in patients with CKD. The Cox regression models 3 shows that the multivariate-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of FT3, FT4 and TSH with the all-cause mortality were 0.66(0.47,0.93), 1.07(1.04,1.10) and 1.01(0.98,1.04). At the same time, FT3/FT4 and TFQI(FT3) were significantly associated with all-cause mortality after multivariate adjustment. And we further converted thyroid function indicators and thyroid homeostasis parameters from a continuous variable to a categorical variable (quartiles) to conduct the sensitivity analysis. There was no difference in cardiovascular mortality. In crude Kaplan-Meier analyses, there was a U-shaped nonlinear relationship between FT3, TSH, FT3/FT4, TT4RI, TT3RI and TSHI with all-cause mortality, but not FT4, TFQI(FT4) and TFQI(FT3). There was an inverted U-shaped relationship between TFQI(FT3) and TT4RI with cardiovascular mortality, but not FT3, FT4, TSH, FT3/FT4, TFQI(FT4), TT3RI and TSHI. CONCLUSIONS: Thyroid function and thyroid parameters are closely related to the prevalence of the CKD and all-cause and cardiovascular mortality among individuals with CKD, and the specific mechanisms still required further in-depth research in the future.