Low vitamin D levels in outpatient postmenopausal women from a rheumatology clinic in Madrid, Spain: Their relationship with bone mineral density

To evaluate a possible relationship between vitamin D levels and bone miner al density (BMD) and the prevalence of hypovitaminosis in a population of p ostmenopausal women from a rheumatologic outpatient clinic in Madrid, Spain , 171 postmenopausal women (aged 47-66 years) divided into two groups (oste oporotic and nonosteoporotic, according to WHO criteria) were studied betwe en November and June. Liver and kidney function were normal in all subjects . Serum parathyroid hormone (PTH) and calcidiol levels were determined and bone densitometry carried out at the lumbar spine and hip level. PTH and ca lcidiol serum levels did not show any correlation. Serum PTH was inversely related to BMD at both hip and lumbar spine in the total group, and at the hip with calcidiol levels lower than 37 nmol/l. Calcidiol was directly rela ted to hip BMD only when levels were lower than 37 nmol/l. Results of a ste pwise multiple regression analysis showed that the single factor which affe cted BMD at the hip was calcidiol in the subgroup with serum calcidiol leve ls below 37 nmol/l, while in the subgroup with serum calcidiol levels above 37 nmol/l, the main factor affecting hip BMD was serum PTH. The prevalence of vitamin D deficiency at a cutoff of 37 nmol/l was 64%. In summary, calc idiol serum levels below 37 nmol/l seem to affect bone mass, regardless of the effect of PTH. Vitamin D deficiency is a frequent finding in the postme nopausal women who attend a rheumatology outpatient clinic in Madrid. Vitam in D supplementation should therefore be considered in this population duri ng the winter season.