Kidney Week

Abstract: FR-PO0265

Vitamin D Metabolite Ratio is a Marker of Osteoid in Persons Across the Spectrum of Kidney Diseases

Session Information

• Bone and Mineral Metabolism: Clinical Epidemiology and Outcomes
  November 07, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Bone and Mineral Metabolism

• 502 Bone and Mineral Metabolism: Clinical

Authors

• Ginsberg, Charles, University of California San Diego, La Jolla, California, United States

Charles Ginsberg, MD, MA

• Hoofnagle, Andrew N., University of Washington, Seattle, Washington, United States

Andrew N. Hoofnagle, MD, PhD

• Salusky, Isidro B., University of California Los Angeles, Los Angeles, California, United States

Isidro B. Salusky, MD, FASN

• Bukata, Susan V, University of California San Diego, La Jolla, California, United States

Susan V Bukata, MD

• Drake, Matthew T, Hospital for Special Surgery, New York, New York, United States

Matthew T Drake, MD, PhD

• Shah, Mita, University of California San Diego, La Jolla, California, United States

Mita Shah, MD

• Nickolas, Thomas L., Washington University in St Louis, St. Louis, Missouri, United States

Thomas L. Nickolas, MD, MS, FASN

• Ix, Joachim H., University of California San Diego, La Jolla, California, United States

Joachim H. Ix, MD, FASN

Background

Severe vitamin D deficiency is associated with osteomalacia and rickets. 25-hydroxyvitamin D [25(OH)D] is the standard clinical biomarker of vitamin D status, although its relationship with osteoid volume, is unclear. Higher concentrations of the vitamin D catabolic product 24,25-dihydroxyvitmin D [24,25(OH)₂D] and a higher ratio of 24,25(OH)₂D₃ to 25(OH)D₃ (the vitamin D metabolite ratio [VMR]) have been shown to be superior predictors of fracture risk and changes in bone density than 25(OH)D alone.

Methods

We measured plasma concentrations of 24,25(OH)₂D₃, 25(OH)D₂, and 25(OH)₂D₃ in 37 persons who underwent clinically indicated bone biopsies for histomorphometry. We used linear regression to assess the relationship of 25(OH)D and the VMR with osteoid measures and markers of bone turnover. We used models adjusting for demographics and estimated glomerular filtration rate (eGFR), kidney transplant status, as well as circulating calcium, phosphate, parathyroid hormone, fibroblast growth factor 23, and calcitriol concentrations.

Results

Thirty-three study participants had adequate biopsy reports for interpretation. The mean age was 64 +/- 11 years, 64% were female, 90% had CKD and 55% had a history of kidney transplant. Two participants were on maintenance hemodialysis and the mean eGFR among all other participants was 48 +/- 23 ml/min/1.73m². In fully adjusted models, a 1% higher VMR was associated with a 1.1% (95% CI 0.2%, 2.2%) lower osteoid volume (Table). A 1% higher 25(OH)D was not associated with osteoid volume [1.2% (-1.1%, 3.4%)]. We found similar relationships with bone turnover markers (Table), although these did not reach statistical significance.

Conclusion

In a cohort of patients undergoing clinical bone biopsy, a lower VMR was associated with greater osteoid while 25(OH)D concentrations were not. The VMR represents a promising marker of bone mineralization status currently lacking in clinical practice. Larger bone biopsy studies are needed to evaluate the utlity of the VMR as a marker of a mineralization defect in persons with kidney disease.

Funding

• NIDDK Support

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025vzxszawa