Excess androgenicity only partially explains the relationship between obesity and bone density in premenopausal women

Obese subjects have increased bone density relative to non-obese subjects yet this relationship is not fully understood. We examined whether alterations in sex hormones or binding proteins might explain the effect of obesity on osteoporosis in 83 premenopausal women from the San Antonio Heart Study, a population-based study of diabetes. We measured total testosterone, oestradiol, oestrone, sex hormone binding globulin (SHBG), and serum dehydroepiandrosterone sulphate (DHEA-SO₄). Bone density was assessed by a Hologic dual photon absorptometer. Lumbar spine and femoral neck density were positively correlated with body mass index (BMI). In addition, femoral neck density was positively correlated with DHEA-SO₄. BMI was negatively correlated with SHBG. After adjustment for sex hormones by multiple linear regression a positive association between bone density and obesity still exists suggesting that the association between obesity and bone density is at least partially independent of sex steroids in premenopausal women.