Endocrine Abstracts

Introduction: Reduced sex hormone binding globulin (SHBG) is seen in patients with polycystic ovarian syndrome (PCOS) and is considered a surrogate marker of hyperinsulinaemia in these patients. Little data currently exists on the biological variability of SHBG for an individual with PCOS and this information is crucial to establish its clinical utility. Method: 12 PCOS patients (median age 28 yrs, range 18-31) and 11 weight matched, control women having regular menses and without PCOS (median age 30 yrs, range 19-33) were recruited. Blood samples were collected after an overnight fast at four day intervals on 10 consecutive occasions. Duplicate samples of stored serum were analysed for SHBG and insulin in a single batch and insulin resistance calculated by the homeostasis model assessment method (HOMA-IR). Results: As expected, in the PCOS patient's SHBG concentrations were lower than in the controls (median 24.8 (IQR 20.2-31.5) vs. 53.8 (32.8-71.5) nmol per Litre, p=0.0001), the insulin levels higher (19.8 (15.1-29.2) vs. 7.75 (6.03-9.16) micro IU per ml, p=0.0001) and the HOMA-IR greater (4.36 (3.2-6.71) vs. 1.65 (1.26-2.00) units, p= 0.0001). The intraindividual variance of SHBG rose linearly with increasing SHBG concentrations (r=0.88, p<0.0001), which in turn meant a trend for SHBG being less variable in PCOS patients than controls (12.6% vs 48.3%, p=0.108). Paradoxically, insulin concentrations (246% vs 5.5%, p=0.004) and insulin resistance (21.6% vs 0.23%, p=0.007) were more variable in the PCOS group than controls. Conclusions: The PCOS subjects were relatively hyperinsulinaemic, insulin resistant and demonstrated lower SHBG levels than controls. However, variable fasting insulin/insulin resistance in PCOS was not reflected in variable SHBG, whereas in controls the opposite held true. Thus, this study has shown that while SHBG concentrations may be inversely associated with levels of insulin/insulin resistance, they are not in close step with one another in either health or polycystic ovarian disease.