MENOPAUSAL BONE LOSS IS PARTIALLY REGULATED BY DIETARY-INTAKE OF VITAMIN-D

Five years ago we reported results from a cross-sectional study of the effect of nutritional factors on calcium-regulating hormones and bone loss in perimenopausal women. We found an inverse correlation between serum 25-hydroxyvitamin D (25OHD) and immunoreactive parathyroid hormone (PTH), and we postulated that over time, women with lower 25OHD would lose more bone because of increased bone remodeling induced by secondary hyperparathyroidism. We have followed 38 of these women for 5 years. Twenty-two have gone through menopause and we are reporting observations on these 22 subjects. Bone mineral analysis was performed twice a year at the distal and mid-radius using single-photon absorptiometry. The slope of the bone mineral content curve was calculated by least squares. Bone loss increased within 6 months of the rise in serum follicle stimulating hormone (FSH) to >40 mIU/ml. We continued to see a negative correlation between 25OHD and PTH (r = -0.450, P = 0.03). Premenopause, PTH was negatively correlated with the proximal bone mineral content (PBMC) slope (-0.604, P = 0.002). The distal bone mineral content (DBMC) 5-year slope was correlated with dietary vitamin D (r = 0.509, P = 0.02), the higher the intake, the less negative the slope. The 5-year PBMC slope was negatively correlated with serum osteocalcin (OC) levels (r = -0.382, P = 0.08). Before menopause, the change in PBMC was positively correlated with OC (r = 0.450, P = 0.03). Postmenopause, the correlation with DBMC slope was negative (r = -0.506, P = 0.05). The results provide further evidence that with uncoupling of bone remodeling after menopause, a high turnover state is associated with greater bone loss. Bone loss accelerates early in menopause, frequently before the cessation of menses. Adequate vitamin D nutritional status preserves bone mass in perimenopausal women by reducing serum PTH concentration and PTH-dependent bone remodeling.