Abstract: FR-PO284

Interactions of Calcium, Vitamin D, and Kidney Function with Parathyroid Hormone Levels

Session Information

Category: Mineral Disease

  • 1202 Mineral Disease: Vitamin D, PTH, FGF-23

Authors

  • McGill, Rita L., University of Chicago, Chicago, Illinois, United States
  • Worcester, Elaine M., University of Chicago, Chicago, Illinois, United States
  • Ennis, Jennifer L., Litholink Corporation, Chicago, Illinois, United States
  • Dhillon-Jhattu, Sangeet, University of Chicago, Chicago, Illinois, United States
  • Coe, Fredric L., University of Chicago, Chicago, Illinois, United States
Background

Parathyroid hormone (PTH) is a crucial factor in regulating calcium homeostasis and bone mineral deposition. Vitamin D and estimated glomerular filtration rate (eGFR) also interact with PTH, and we aimed to better characterize the interplay between these factors.

Methods

Laboratory results performed at LabCorp between April 2011 and February 2014 were assessed, if simultaneous PTH, calcium, vitamin D and eGFR were available. Calcium and vitamin D were categorized, and analyses were stratified for National Kidney Foundation stage of chronic kidney disease (CKD). Percentages of tests in which a PTH>65 was observed were calculated and plotted for each combination of calcium, vitamin D, and eGFR.

Results

Among 126,615 patients, 38% were male and mean age was 65.6 years. Compared to those withe GFR>90, PTH levels were more likely to be abnormal in CKD stages 2 and 3A. Higher vitamin D levels were associated with lower PTH in all patients, and this effect became more prominent with decreasing eGFR. The normal U-shaped relationships between calcium and PTH were distorted in CKD stages 4 and 5.

Conclusion

PTH levels become detectably abnormal even in very early CKD. Repletion of vitamin D to levels of 40 ng/mL or greater reduces PTH in patients with eGFR ≥ 15.

Percentage of Patients with PTH > 65, by Calcium, Vitamin D, and Chronic Kidney Disease Stage