Association Between Sex Hormone Binding Globulin and Metabolic Syndrome in US Adults: Insights from National Health and Nutrition Examination Survey (NHANES) 2013-2016

Background: Metabolic syndrome (MetS) presents a notable public health challenge on a global scale, exerting a considerable impact on individuals' health and quality of life. There is mounting evidence indicating a robust association between MetS and levels of sex hormones. Therefore, the study aims to explore the relationship between sex hormone binding-globulin (SHBG) and MetS, and to provide evidence that could inform the development of effective prevention strategies for MetS.

Methods: Data for this cross-sectional investigation were collected during the 2013-2016 cycle of the National Health and Nutrition Examination Survey (NHANES), from which 5,499 adults were sampled. The criteria established by the Adult Treatment Program III of the National Cholesterol Education Program were utilized to define MetS. SHBG levels were measured using a standardized technique. Multivariate-adjusted logistic regression, multivariate restricted cubic spline, and threshold effect analyses were utilized to investigate the association between SHBG levels and MetS. Moreover, the stratified analyses and interaction tests of covariables were presented in a forest plot. Finally, sensitivity analysis was utilized to ensure the robustness of the results.

Results: Overall, 1822 participants had MetS. After adjusting for possible confounders, SHBG levels were associated with MetS (Odds ratio [OR], 0.984; 95% confidence interval [CI], 0.981-0.986; P < 0.01). The multivariate restricted cubic spline analysis demonstrated a non-linear association between SHBG and MetS (P < 0.001). With two piecewise regression models, the adjusted OR of developing MetS was 0.964 (95% CI, 0.959-0.969; P < 0.001) among people with SHBG < 76.653 nmol/L, but there was no correlation between SHBG and MetS in participants with SHBG ≥ 76.653 nmol/L. The stability of the association between SHBG levels and MetS was confirmed using subgroup analysis and sensitivity analyses.

Conclusions: Our results suggest that reduced SHBG levels are associated with an increased prevalence of MetS in adults, particularly when SHBG levels are below 76.653 nmol/L. More investigation is required to understand comprehend the mechanisms underlying these results and to delve into their clinical implications.