Correlation between sex hormone binding globulin and total testosterone and insulin resistance in polycystic ovary syndrome

Objective To investigate the effect of sex hormone binding globulin (SHBG) and total testosterone (TT) on predicting insulin resistance (IR), reproductive endocrine hormones, carbohydrate and lipid changes in polycystic ovary syndrome (PCOS) patients. Methods Three hundred forty–four cases of PCOS and 100 cases of normal women cellected from June 2004 to May 2006 in the Obstetrics and Gynecology Hospital of Fudan University were included in the study, the mean age was (23±5) years, the levels of SHBG and TT in serum were compared between PCOS and normal control, the correlation between SHBG/TT and basal body index, waist to hip ratio, endocrine hormone, lipids and glucose profile were analyzed by Spearman correlation. The impact of age, ovarian volume, leuteinizing hormone(LH), follicle stimulating hormone(FSH), LH/FSH ratio, TT, SHBG, dehydroepiandrosterone–sulphate, prolactin and cortisol on IR were analyzed by Logistic regression. A receiver operating characteristic(ROC) curve between SHBG and IR were taken and acquired a cut–off point, difference between groups with higher/lower SHBG were compared. Results SHBG was lower in PCOS group than in normal control ((114±88) vs (201±106) mmol/L, t=–5.60, P<0.01) and TT was higher in PCOS than in normal control ((2.8±1.0) vs (1.7±0.6) nmol/L, t=7.73, P<0.01), the difference had significantly statistic mean. SHBG had an inverse correlation with fasting plasma insulin, insulin area under curve, glucose area under curve, homeostasis model assessment insulin resistance, triglycerides and waist–hipo ratio(r=–0.30, –0.26, –0.29, –0.19, –0.20, –0.29, –0.22, respectively, all P<0.01). Total testosterone had a positive correlation with fasting plasma insulin (r=0.14, P<0.01), all the point of insulin releasing test (1, 2, 3 h r=0.15, 0.12, 0.11, respectively, all P<0.05), the corresponding insulin area under curve(r=0.15, P<0.05)and homeostasis model assessment insulin resistance(r=0.11, P<0.05). Logistic regression demonstrated that SHBG was an independent predictor of IR(OR=3.741). A SHBG level of 88 mmol/L(95%CI: 0.668 to 0.774) was used as the cut–off point for predicting IR according to the ROC curve.Fasting plasma insulin, insulin area under curve, homeostasis model assessment insulin resistance, fasting plasma glucose, glucose area under curve were higher in patients with SHBG<88 mmol/L than those SHBG≥88 mmol/L(t=–6.45, –5.08, –6.19, –3.16, –3.66, respectively, all P<0.01), the same trend as triglycerides(t=–2.06, P<0.05). Conclusions TT in serum is higher in PCOS women while SHBG on the control. TT has a positive correlation and SHBG has a negative correlation with IR in PCOS. SHBG is perhaps the only independent risk factor to predict IR in PCOS women. Key words: Polycystic ovary syndrome; Sex hormone binding globulin; Insulin resistance; Total testosterone; Correlation