We measured plasma sex hormone-binding globulin (SHBG), corticosteroid-binding globulin (CBG), and total cortisol, and calculated free plasma cortisol in 1 137 subjects attending a hospital outpatient lipid disorders clinic to investigate whether or not these analytes correlated with the degree of insulin resistance and the presence of the metabolic syndrome. In both males and females, plasma SHBG correlated inversely with anthropometric measures and with fasting glucose, insulin, insulin resistance, and triglycerides, and positively with HDL-cholesterol. However, in males with the metabolic syndrome, unlike females, the relationship between SHBG, some anthropometric measures, fasting glucose, insulin, and HDL-cholesterol were lost, which suggests that in males SHBG may not co-cluster with other components of the metabolic syndrome. In males and males with the metabolic syndrome, total plasma cortisol and calculated plasma free cortisol correlated positively with fasting glucose. Corticosteroid-binding globulin correlated inversely with percentage body fat and positively with HDL-cholesterol in males with and without the metabolic syndrome. CBG correlated negatively with age in both sexes. Overall, the results confirm the finding that SHBG is a marker of insulin resistance in males and females and that SHBG is associated with fasting triglycerides in males with the metabolic syndrome. Importantly, SHBG could be considered a stronger component of the metabolic syndrome in females than in males. However, the aetiological role of CBG and cortisol in insulin resistance is uncertain, although in males, cortisol and CBG could be subtly related to the degree of insulin resistance.
Georg Thieme Verlag KG Stuttgart New York.