Calcium isotope ratio (δ44/42Ca) reflects kidney function and calcium excretion but not bone mineral density or bone turnover: a cross-sectional study
Authors' conclusion
While δ44/42Ca reflects aspects of calcium metabolism, such as nutritional calcium supply, in this real-world setting, it failed to predict fractures or distinguish osteoporosis from healthy controls or osteopenia and vice versa, indicating limited clinical use.
Study context
- Population
- Patients with osteoporosis and osteopenia, with controls43 controls
- Participants
- 301 patients
- Outcome
- Serum and urine δ44/42Ca as a biomarker of bone metabolism, vs bone (incl. bone density) and treatment parameters
Methodological detailsreal-world setting
- Real-world setting
Main finding
As reported in the abstract
Correlation of δ44/42Ca with urinary calcium excretion
- Serum δ44/42Ca vs urinary calcium excretion, r²
- 0.55
- Urine δ44/42Ca vs urinary calcium excretion, r²
- 0.20
- P for correlation
- p<0.0001
Observational data: associations, not effects.
Further findings
Factors affecting δ44/42Ca
- Higher β-CTX associated with low δ44/42Ca
- P < 0.05
- Age, kidney function and calcium intake significantly affected δ44/42Ca
Treatment effects on δ44/42Ca
- Osteoanabolic therapy increased δ44/42Ca
- P < 0.05
- Antiresorptive treatment had no effect
δ44/42Ca by fracture, BMD and age-adjusted stratification
- Above age-adjusted δ44/42Ca threshold: higher urinary calcium and PTH (both)
- P < 0.0001
- No differences in δ44/42Ca by fracture or BMD stratification
- Pattern consistent with neutral or positive bone mineral balance
Original publication
Calcium isotope ratio (δ44/42Ca) reflects kidney function and calcium excretion but not bone mineral density or bone turnover: a cross-sectional study. Osteoporos Int. Published 11 April 2026. doi:10.
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