Combined effects of sex hormone-binding globulin and sex hormones on risk of incident type 2 diabetes

Background: The aim of the present study was to investigate the combined effects of sex hormone-binding globulin (SHBG) and sex hormones on the risk of type 2 diabetes (T2D).

Methods: A nested case-control study of Chinese participants in the Environment, Inflammation and Metabolic Diseases Study (2008-13) was performed. Of the 3510 subjects free of diabetes, 145 men and 87 women developed diabetes over the 5-year follow-up. One age- and sex-matched control subject was selected for each case. Baseline concentrations of SHBG, estradiol, testosterone, and dehydroepiandrosterone sulfate (DHEA-S) were divided into tertiles and subjects were classified as having low, intermediate and high levels accordingly.

Results: After multivariate adjustment, men with low SHBG levels had a fourfold greater risk of T2D than men with high SHBG levels. Conversely, men with high estradiol levels had a fourfold greater risk of T2D than men with low estradiol levels. Men with low SHBG + high estradiol had a 20-fold greater risk of T2D than men with high SHBG + low estradiol (odds ratio [OR] 20.23; 95% confidence interval [CI] 4.62-51.33). These risk associations in men were not observed for testosterone or DHEA-S, alone or in combination with SHBG. Compared with low SHBG, the risk of T2D decreased with increasing SHBG tertile (OR 0.92 [95% CI 0.21-4.53], 0.14 [95% CI 0.10-0.74]; Ptrend = 0.043) after multivariate adjustment in women. Estradiol, testosterone, and DHEA-S levels showed no association with T2D in women.

Conclusion: Low SHBG in conjunction with high estradiol has an additive detrimental effect on the risk of T2D in men.