Is sex hormone-binding globulin associated with glucose tolerance?

Background/aim Women with a reduced concentration of sex hormone-binding globulin (SHBG) in the first trimester of pregnancy are at increased risk of developing gestational diabetes. Furthermore, a lower concentration of SHBG in women with gestational diabetes identifies women at increased likelihood of requiring insulin treatment. The aim of this study was to explore the relationship of SHBG concentration in pregnancy to insulin resistance and glucose tolerance. Methods Prospective cohort study of 220 pregnant women who attended The Royal North Shore Hospital in Sydney, Australia between August 2002 and June 2003 for their 75-g glucose tolerance test. All tests were performed in the morning after the women had fasted for at least 10 h. To test for differences between patients with or without gestational diabetes, t-tests and chi-square tests were used. Stepwise linear regression was used to determine the independent predictors of SHBG. Results The mean concentration of SHBG increased linearly with gestational age. Statistically significant predictors of SHBG from the stepwise regression were gestational age (P < 0.001), insulin resistance (P < 0.001) and body mass index (P = 0.003). Glucose tolerance as assessed by either a fasting or 2-h glucose tolerance test did not predict SHBG concentration in this population. In addition, there was no significant difference in the concentration of SHBG between patients categorized as normal glucose tolerance or gestational diabetes (P = 0.77). This remained the case when SHBG was expressed as SHBG/insulin ratio as suggested by Bartha et al. (Sex hormone-binding globulin in gestational diabetes. Acta Obstet Gynecol Scanda 2000; 79: 839-845) (P = 0.10). Conclusion In a cross-sectional study of pregnant women, we find no association between SHBG concentration and glucose tolerance.