Association between Mammographic Breast Density and Markers of Calcium Metabolism in Women: A Retrospective Observational Study

Aim: The aim of this study was to assess the relationship between mammographic breast density and biochemical indices of calcium metabolism, as well as femoral neck bone mineral density (BMD) in women aged 40-80 years. Material and Methods: In this retrospective, single-center study, 598 women undergoing screening mammography between November 2020 and March 2025 were included. After applying exclusion criteria, 200 age-matched women were randomly selected and evenly stratified into four BI-RADS breast composition categories (A, B, C, and D), 50 women in each. Serum vitamin D3, parathyroid hormone (PTH), calcium, and femoral neck t-scores were retrieved from institutional records and compared between these four categories. Results: Vitamin D3 levels (p=0.021) and femoral neck t-scores (p=0.041) were found to be significantly different between four categories. Post hoc analysis demonstrated significantly different vitamin D3 concentrations in the Category D compared with categories A (p=0.021), B (p=0.032), and C (p=0.048). Femoral neck t-scores progressively decreased in Category D compared to categories A (p=0.013), B (p=0.025), and C (p=0.041). No significant differences were observed for PTH (p=0.589) or serum calcium (p=0.441). Conclusion: Higher mammographic breast density was associated with lower vitamin D3 concentrations and reduced femoral neck BMD. Breast composition may serve as a readily available imaging biomarker to identify women at increased risk of vitamin D deficiency and osteoporosis, and has potential integration into individualized risk stratification strategies.