Influence of age and gender on associations of body mass index with bone mineral density, bone turnover markers and circulating calcium-regulating and bone-active sex hormones

Abstract Although it is well known that body mass index (BMI) and bone mineral density (BMD) are positively correlated, the mechanisms by which adiposity reduces the risk of osteoporotic fractures are not fully understood. The present study was initiated to gain deeper insight into the mechanisms underlying the osteoprotective effect of adiposity, and to assess particularly the relevance that BMI-associated changes in circulating hormone levels could have for the build-up of additional bone mineral density. Using data from a previous study on a large cohort of healthy adult Austrians, we analyzed correlations of BMI with (i) BMD at sites in the lumbar spine and hip region, (ii) bone resorption and formation markers, (iii) circulating levels of vitamin D, parathyroid hormone, testosterone and estrogen, and (iv) rates of daily vitamin D and calcium intake. After adjustment for age, positive correlations between BMI and BMD were highly significant ( P P P P P P P P P