Serum 25-Hydroxyvitamin D, Calcium-Phosphate Profile, and Bone Mineral Density Across Normal, Osteopenic, and Osteoporotic Adults: A Hospital-Based Cross-Sectional Study

Background: This study evaluated the association of serum 25-hydroxyvitamin D (25(OH)D) with bone mineral density (BMD), skeletal status, serum calcium, and serum phosphate among adults undergoing bone health assessment. Methods: This hospital-based cross-sectional study was conducted in the Department of Biochemistry at the Meenakshi Medical College Hospital and Research Institute, Kanchipuram, India, from January 2025 to December 2025. Ninety adult participants with complete biochemical and dual-energy X-ray absorptiometry (DXA) data were included. Adults aged 40 years or older with complete biochemical and DXA data were included. Participants were classified as vitamin D sufficient, insufficient, or deficient, with 30 individuals in each group. Skeletal status was categorized as normal, osteopenia, or osteoporosis using standard T-score criteria. Data were analyzed using chi-square and one-way analysis of variance. Results: Normal BMD was observed more frequently in the vitamin D-sufficient group, whereas osteopenia and osteoporosis were more frequent in the vitamin D-insufficient and vitamin D-deficient groups (p < 0.001). Mean serum 25(OH)D, BMD, serum calcium, and serum phosphate were lower across osteopenia and osteoporosis categories than in the normal BMD category. Mean age did not differ significantly across skeletal categories. Conclusions: In this selected hospital-based cross-sectional cohort, lower serum 25(OH)D levels were observed among participants with osteopenia and osteoporosis than those with normal BMD. These findings suggest that biochemical parameters may be interpreted alongside densitometric assessment, while recognizing the limitations of the cross-sectional design and lack of confounder adjustment.