ENDOCRINE AND PHYSICAL DETERMINANTS OF BONE MASS IN LATE POSTMENOPAUSE

To analyze the relative contribution of endocrine and physical factors to bone mineral density (BMD) in late menopause, we studied biochemic al markers of bone turnover as well as sex and calciotropic hormones i n 53 women (mean age 61 +/- 5.3 years), 5 to 23 years after natural me nopause. BMD was measured at the lumbar spine and proximal femur by du al energy radiography. Stepwise regression analysis showed that age an d PTH levels were the two major factors that significantly accounted f or spinal BMD, with a final r(2) = 0.27. Plasma androstenedione was th e only other variable that contributed, albeit not significantly, to s pine BMD increasing the r(2) by 2%. Conversely, body mass was the main contributor to femoral BMD at all sites. While serum calcium and urin ary hydroxyproline were significant determinants of neck BMD, urinary hydroxyproline and age provided significant source of variation for tr ochanteric BMD, and circulating FSH for BMD in the Ward's area. The fi nal models gave r(2) values of 0.35, 0.31, and 0.23, for neck, trochan ter and Ward's areas, respectively. Thus, determinants of bone density differentially affect the vertebral and proximal femoral sites. While increasing age and PTH, probably reflecting a subclinical vitamin D d eficiency, explain a decreased vertebral bone density, body mass appea rs to affect mostly the proximal femur. Circulating androgens play a s econdary role. A persistently increased bone turnover state is conduci ve to lower bone density in late postmenopausal women.