Relationship of sex hormone binding globulin to overall adiposity and body fat distribution in a biethnic population.

Previous data have indicated that decreased sex hormone binding globulin (SHBG) is associated with increased overall and upper body adiposity and higher levels of glucose, insulin and triglyceride (TG) and decreased levels of high-density lipoprotein (HDL) cholesterol. Since Mexican Americans have greater overall and upper body adiposity, higher rates of non-insulin-dependent diabetes mellitus, higher TG and lower HDL levels than non-Hispanic whites, we postulated that they would also have lower levels of SHBG. We measured total testosterone and total estradiol using a commercial radioimmunoassy and SHBG using a dextran-coated charcoal technique in premenopausal women (61 Mexican American and 39 non-Hispanic white) as part of the San Antonio Heart Study, a population-based study of diabetes and cardiovascular risk factors. There were no significant ethnic differences in total testosterone or total estradiol. SHBG, however, was lower in Mexican American (0.285 micrograms/dl) than in non-Hispanic white women (0.429 micrograms/dl) (P = 0.009). After adjustment for body mass index (BMI), ratio of waist-to-hip circumference (WHR) and ratio of subscapular-to-triceps skinfolds (centrality index), SHBG remained lower in Mexican Americans (0.307 micrograms/dl) than in non-Hispanic whites (0.396 micrograms/dl), although this difference was no longer statistically significant (P = 0.083). BMI, WHR and centrality index were all negatively associated with SHBG (P less than 0.01). The lower levels of SHBG in premenopausal Mexican American women compared to non-Hispanic white women may reflect greater in-vivo androgenicity and may be related to a variety of metabolic abnormalities seen in this ethnic group.