Sex Hormone Binding Globulin, Body Fat Distribution and Insulin Resistance in Premenopausal Women

Lee, Young Sook; Lee, Hye Jin; Oh, Jee Young; Hong, Young Sun; Sung, Yeon Ah

Abstract

BACKGROUND: Low levels of sex-hormone binding globulin (SHBG), an indirect index of androgenicity, have been reported to be associated with obesity, especially central obesity. In women, increased androgenicity is related to hyperinsulinemia, impaired glucose tolerance and the development of type 2 diabetes mellitus. Recent studies have suggested that the relationship between SHBG and insulin resistance was mediated by the change in total or visceral adiposity, and that ethnical differences in the relationship between sex hormone and body fat distribution might exist.
METHODS
We examined the associations of SHBG to the body fat distribution and insulin resistance in Korean premenopausal women. The fasting serum level of SHBG was measured by RIA, and the insulin sensitivity by the minimal model derived sensitivity index (SI), using the insulin modified intravenous glucose tolerance test. The amount of body fat, and its distribution, were assessed by anthropometric measurement, bioelectric impedance analyses, and computed tomography at the level of the umbilicus.
RESULTS
1. SHBG was significantly inversely correlated with the body mass index (BMI), waist circumference, visceral fat area, and fasting insulin levels, and was significantly positively correlated to the SI. 2. SHBG was significantly lower in premenopausal women with an impaired glucose tolerance, compared to those with a normal glucose tolerance, and significantly lower in those with hypertension (systolic BP> or =140 mmHg or diastolic BP> or =90 mmHg), compared to those with normal blood pressure. SHBG was also significantly lower in persons with central obesity(waist circumference > or = 80 cm) compared to those without. 3. In a multiple linear regression analysis, the SI was significantly associated with SHBG, after adjustment for age, BMI, systolic blood pressure, triglycerides, HDL- cholesterol, and percentage body fat, but this association disappeared after additional adjustment for visceral fat area. 4. In a multiple linear regression analysis, the fasting plasma insulin, BMI and percentage body fat were significant independent factors associated with SHBG.
CONCLUSION
Increased androgenicity as assessed by decreased serum SHBG concentrations, is strongly associated with an unfavorable body fat distribution, hypertension, glucose intolerance, hyperinsulinemia, and insulin resistance.