Vitamin D and parathyroid hormone in relation to bone mineral density in postmenopausal women

Despite vitamin D insufficiency being widely reported, in Serbia the epidemiological data lack information regarding vitamin D status in the sera of postmenopausal women. The aim of this study was to establish the prevalence of inadequate serum 25-hydroxyvitamin D [25(OH)D] concentrations in postmenopausal Serbian women with seasonal variations of 25(OH)D, in relation to parathyroid hormone (PTH) and bone mineral density (BMD).

A total of 95 postmenopausal women, mean age 65.1 +/- 9.08 years, were examined. Measurements of 25(OH)D and PTH were performed both in the winter and the summer period, using electrochemiluminiscence immunoassays. BMD (g/cm2) was measured by the dual-energy x-Ray absortimetry (DXA) method on the spine and hip areas.

A decreased value of vitamin D (< 75 nmol/L) in 88.4% of postmenopausal women and an elevated level of PTH (> 65 pg/mL) in 25.3% of the cases were found. Elevated PTH varied individually, but was mostly increased if 25(OH)D was equal or lower than 37.6 nmol/L. 25(OH)D insufficiency was found in winter in 94.5% and in summer in 80% of the cases (p < 0.01). The mean of the PTH was higher (p < 0.05) in winter than in summer. A significant negative correlation between 25(OH)D and PTH (p < 0.001) was proved. Correlation between 25(OH)D and PTH with BMD at lumbar spine was established in the whole group, but at the femoral neck in women aged over 65 years (p < 0.05).

Our results showed a high prevalence of vitamin D insufficiency (88.4%) among postmenopausal women. The levels of 25(OH)D and PTH changed significantly according to the season.