Associations of Total Testosterone and Sex Hormone–Binding Globulin Levels With Insulin Sensitivity in Middle-Aged Finnish Men

While sex hormone–binding globulin (SHBG) production in the liver is mainly regulated by sex steroids and thyroxine, insulin is suggested to be another important regulator, and a low SHBG level is a marker of insulin resistance (1) and, consequently, a predictor of type 2 diabetes (2). The role of testosterone, another risk marker of type 2 diabetes, has been insufficiently clarified (2). Further, only one earlier study (3) has found evidence suggesting that, compared with total testosterone, high SHBG may be a more powerful correlate of insulin sensitivity, mediating the link between total testosterone and insulin sensitivity. We investigated the contribution of SHBG to the association between total …