VITAMIN-D STATUS AND SEX-HORMONE BINDING GLOBULIN - DETERMINANTS OF BONE TURNOVER AND BONE-MINERAL DENSITY IN ELDERLY WOMEN

To examine the relation of the vitamin D status and the remaining estr ogen activity with bone turnover and bone mineral density (BMD) in eld erly women, BMD was measured at both hips using dual-energy X-ray abso rptiometry and at the distal radius using single photon absorptiometry , in 330 healthy women aged 70 and over, Vitamin D metabolites, sex ho rmone binding globulin (SHBG), PTH(1-84), osteocalcin, alkaline phosph atase, and hydroxyproline and calcium excretion in 2 h fasting urine w ere measured, Multiple linear regression was used to adjust for potent ial confounders, In 65% of the women, serum 25(OH)D was below 30 mmol/ l, Only values below a threshold for 25(OH)D were negatively related t o serum PTH(1-84) (p = 0.02, threshold at 25 nmol/l) and to osteocalci n levels (p = 0.04, threshold at 30 nmol/l), BMD of the femoral neck a nd trochanter was positively related to serum 25(OH)D (left neck p = 0 .001) with thresholds at 30 nmol/l whereas the distal radius was not ( p = 0.32), Serum PTH was negatively related to BMD at all measurement sites (all p < 0.001), Serum SHBG, an inverse measure of estrogen acti vity, was positively related to osteocalcin levels (p = 0.004) and the urinary hydroxyproline/creatinine ratio (p = 0.002) and negatively re lated to the BMD of the trochanter (left trochanter p = 0.02) and the distal radius (p = 0.001), We conclude that in elderly women, serum 25 (OH)D levels below 30 nmol/l are associated with secondary hyperparath yroidism and increased bone turnover, SHBG is positively related to bo ne turnover, Vitamin D deficiency especially influences BMD of the fem oral neck, a cortical area, SHBG mainly influences BMD at the trochant eric region and distal radius, predominantly trabecular areas, which m ay reflect the effects of remaining estrogen activity.