Comparison of Serum 25-Hydroxyvitamin D Levels and Bone Turnover Biomarkers in Postmenopausal Women with and without Primary Osteoporosis: A Case-Control Study

Abstract

Abstract: Introduction: The risk of osteoporosis and its fractures increases with ageing, especially in postmenopausal women. The purpose of this study was to compare the serum levels of 25-hydroxyvitamin D (25 (OH) D), BTMs (Alkaline phosphatase (ALP), osteocalcin (OC)) and osteopontin (OP)) in postmenopausal women with and without normal Bone Mineral Density (BMD). Methods: This observational study was conducted on 240 eligible postmenopausal women aged 50-65 years. 120 women with and 120 women without normal-BMD were selected based on the dual-energy X-ray absorptiometry. The serum concentration of BTMs and 25 (OH) D were assessed by ELISA. Receiver-operator characteristics curves (ROC) were used to calculate the area under the curve (AUC). Data were analyzed using Chi-square, independent t-test, Fishers exact test, Binary logistic regression, and linear regression model by SPSS/21. Results: There was no significant difference between mean serum (SD) levels of vitamin D3 in healthy women 47.3 (7.25) ng/ml and low BMD 45.9 (5.21) ng/ml (p=0.657). The mean (SD) OC levels in healthy and low BMD women were 16.1 (6.5) ng/ml and 27.1 (11.7) ng/ml, respectively, and for OP were 25.5 (6.6) ng/ml and 31.4 (5.6) ng/ml, respectively (p<0/001). The mean (SD) ALP was 174.3 (48.6) and 191.4 (55.4), respectively (p=0.013). The adjusted odds ratio (95% CI) for low BMD significantly increased in terms of OC (1.134 (1.086 to 1.184)), OP (1.180 (1.105 to 1.261), (p<0/001)), and ALP (1.007 (1.001 to 1.041), (p=0.024)). Based on ROC analysis, at the cut-off point of 16.28 ng/mL for OC, the sensitivity was 70.3% and the specificity was 70.9%, and at the cut-off point of 28.85 ng/ mL for the OP, the sensitivity was 70.3% and the specificity was 66.6%. Conclusion: Higher serum levels of OC, ALP, and OP were associated with low-BMD. OP and OC had fair diagnostic value for postmenopausal low-BMD. These BTMs may be recommended as screening tests for bone loss and probable bone fracture.