Nonlinear association of sex hormone-binding globulin levels and chronic kidney disease, an analysis based on the National Health and Nutrition Examination Survey (NHANES) 2013–2016

Studies on the relationship between serum sex hormone-binding globulin (SHBG) levels and chronic kidney disease (CKD) remain limited and inconclusive. Therefore, this study aims to evaluate the effects of SHBG on CKD in a nationally representative population. We included a total of 7713 adults from the National Health and Nutrition Examination Survey (NHANES) conducted between 2013 and 2016. Multivariate logistic regression models were utilized to evaluate the association between SHBG levels and CKD, and odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Additionally, we employed a restricted cubic-spline regression model to explore potential dose-response associations. Among the participants, 4030 (52.2%) were women, and CKD was observed in 13.50% (1043/7713). After adjusting for various variables, SHBG levels were found to be associated with the risk of CKD (OR: 1.24; 95% CI: 1.11-1.38), indicating a 24% higher risk of CKD for SHBG levels (log2-transformed). A comparison between the highest quartile (Q4) and the lowest quartile (Q1) of SHBG levels revealed an OR of 1.51 (95% CI: 1.17-1.95) for CKD prevalence. Notably, while the association between SHBG and the risk of CKD disappeared when SHBG levels were <46.1 nmol/l, it existed when SHBG levels exceeded 46.1 nmol/l. Taken together, these findings indicate nonlinear correlations between serum SHBG levels and CKD, with the inflection point occurring at approximately 46.1 nmol/l, which suggest that SHBG levels could serve as a useful marker for assessing CKD risk, with potential applications in early detection and management strategies.