SHBG Levels Do Not Correlate with Insulin Levels in PCOS with Appropriate Fasting Insulin Sensitivity

Abstract

Introduction: There are several phenotypes of polycystic ovarian syndrome (PCOS), and the different phenotypes may differ metabolically. Methods: In the present retrospective study, women with PCOS having normal fasting insulin sensitivity (n = 88) were compared with women with PCOS showing impaired insulin sensitivity (n = 46) using the HPCOS (Hungarian Polycystic ovarian syndrome) database. Results: The impaired insulin sensitivity group has significantly higher body mass index (BMI) and HOMA index than the normal fasting insulin sensitivity group (BMI (kg/m²): 22.0 vs. 28.1, p < 0.0001, HOMA index: 0.96 vs. 2.38, p < 0.0001). The sex hormone binding globulin (SHBG) level was significantly lower, and the free androgen index proved itself significantly higher in the impaired insulin sensitivity group (p < 0.05). Linear regression analysis showed a negative association of BMI with SHBG levels in both groups, while BMI had a positive correlation with insulin concentrations in both groups. However, the SHBG levels were negatively associated with insulin concentrations in the impaired insulin sensitivity group, but this inverse association could not be observed in the normal fasting insulin sensitivity group. Conclusions: The inverse linear correlation of SHBG with HOMA index and serum insulin level is not evident in all PCO syndrome phenotypes, thus SHBG has limited applicability for characterizing carbohydrate metabolism and serum insulin sensitivity.

Keywords: SHBG; insulin resistance; insulin sensitivity; polycystic ovarian syndrome.

Figure 1

Androgenic parameters. (A) Testosterone levels. Testosterone levels did not differ among the groups. (B) SHBG levels. The impaired insulin sensitivity group had significantly lower SHBG level than the normal insulin sensitivity group. (C) Free androgen index. The FAI was significantly higher in the impaired insulin sensitivity group than in the normal fasting insulin sensitivity group. Data presented as median with 95% confident interval confidence interval. Mann–Whitney test, * p < 0.05; *** p < 0.001.

Figure 2

SHBG–BMI–insulin correlations. (A) SHBG–BMI correlations in normal fasting insulin sensitivity group. Pearson correlations, r = −0.5388; r2 = 0.2903; p = 0.0010; β = −5.120 (−8.003 to −2.238). (B) SHBG–BMI correlations in impaired insulin sensitivity group. Pearson correlations, r = −0.5207; r2 = 0.2711; p = 0.0064; β = −1.902 (−3.217 to −0.5883). (C) Insulin–BMI correlation correlations in normal insulin sensitivity group. Pearson correlations, r = 0.4643; r2 = 0.2156; p = 0.0005; β = 0.2344 (0.1074 to 0.3614). (D) Insulin–BMI correlations in impaired insulin sensitivity group. Pearson correlations, r = 0.3283; r2 = 0.1078; p = 0.0473; β = 0.4087 (0.0052 to 0.8122). (E) SHBG–Insulin correlation correlations in normal insulin sensitivity group. Pearson correlations, r = −0.1230; r2 = 0.015; p = 0.385; β = −2.455 (−8.082 to 3.172). (F) SHBG–Insulin correlations in impaired insulin sensitivity group. Pearson correlations, r = −0.4283; r2 = 0.1834; p = 0.0182; β = −3.949 (−7.174 to −0.7237).