Correlations between bone turnover markers, serum magnesium and bone mass density in postmenopausal osteoporosis

Bone mass density (BMD) is still the gold standard for the diagnosis of osteoporosis, but bone turnover markers (BTMs) can provide helpful information regarding the bone remodeling process. The aim of this study was to determine the correlations between BMD and serum levels of BTMs (tartrate-resistant acid phosphatase-5b [TRAP-5b]), bone-specific alkaline phosphatase (BSAP), estradiol (E₂), and magnesium (Mg^[2+]) ion concentrations in postmenopausal osteoporotic women as compared to healthy postmenopausal subjects.

The study included 132 women with postmenopausal osteoporosis and 81 healthy postmenopausal women without osteoporosis. Dual-energy X-ray absorptiometry scan assessed BMD at different skeleton sites. Serum levels of E₂, BSAP, and TRAP-5b were measured by enzyme linked immunosorbent assay. Serum levels of Mg⁽²⁺⁾ were determined using the colorimetric spectrometry technique.

Serum levels of BTMs were significantly higher in osteoporotic women than in controls. BSAP has a moderate sensitivity (76.5%) and specificity (84.3%) (cutoff point 21.27 U/L). At a cutoff point of 3.45 U/L, TRAP-5b presented a sensitivity of 86.3% and a higher specificity of 90.6%. Osteoporotic patients showed significantly lower concentrations of serum Mg⁽²⁺⁾ than the control group. Mg⁽²⁺⁾ levels correlated positively with BMD values (r=0.747, P<0.0001). Furthermore, Mg⁽²⁺⁾ concentrations correlated positively with E₂ levels (r=0.684, P<0.0001). Spine BMD correlated negatively with BSAP levels (r=-0.36, P<0.0001).

Our study showed that BMD correlates negatively with BTMs and positively with E₂ and Mg⁽²⁺⁾ levels. TRAP-5b presents a good specificity in identifying patients with postmenopausal osteoporosis.