The differential effects of serum 25-hydroxyvitamin D 25(OH)D and calcium on trabecular versus cortical bone in postmenopausal osteoporosis remain unclear. This study evaluated their associations with compartment-specific bone mineral density (BMD) using peripheral quantitative computed tomography (pQCT). This cross-sectional study enrolled 100 postmenopausal women (aged 55–69 years) at LLRM Medical College and SVBP Hospital (May 2023–April 2024). Serum 25(OH)D and calcium were assayed biochemically; trabecular, cortical, and total volumetric BMD with bone strength index (BSI) were measured by pQCT (Stratec XCT 2000) at the distal radius. Pearson correlation and multivariable linear regression (adjusted for age, BMI, years since menopause, calcium, comorbidities) were performed. Mean age was 61.85 ± 4.24 years; duration since menopause, 14.50 ± 5.79 years. 25(OH)D deficiency (< 20 ng/mL) occurred in 48%; 55% had calcium < 8.5 mg/dL. 25(OH)D correlated significantly with cortical BMD ( r = 0.513, p < 0.001) but not with trabecular ( r = 0.027, p = 0.788) or total BMD ( r = 0.067, p = 0.506). Conversely, calcium showed a strong correlation with trabecular BMD ( r = 0.534, p < 0.001) and a weaker but significant correlation with cortical BMD ( r = 0.231, p = 0.021). Neither correlated significantly with BSI. On multivariable regression, calcium (β = 8.61, p < 0.001) and years since menopause (β = 1.75, p < 0.001) independently predicted trabecular BMD (adjusted R² = 0.871), while age (β = 5.39, p < 0.001) and calcium (β = 13.98, p = 0.010) predicted cortical BMD (adjusted R² = 0.280). Regression models for total BMD and BSI were non-significant. Multivariable regression identified serum calcium and years since menopause as independent predictors of trabecular BMD, while age—perfectly collinear with serum 25(OH)D in this cohort—and serum calcium independently predicted cortical BMD. Serum 25(OH)D and calcium are differentially associated with bone compartments, with 25(OH)D predominantly linked to cortical bone and calcium to trabecular bone. The high prevalence of both deficiencies supports routine screening and combined supplementation for comprehensive osteoporosis prevention in postmenopausal women.
Mishra et al. (Sat,) studied this question.