Vitamin D and parathyroid hormone status in community-dwelling elderly patients with mild-to-moderate kidney impairment

Introduction: Evidence on vitamin D and parathyroid hormone (PTH) status in patients with early kidney impairment is limited. We aimed to determine the associations among kidney function, vitamin D, and PTH status in community-dwelling elderly patients with mild-to-moderate kidney impairment. Methods: Community-dwelling elderly patients were enrolled in this Institutional Review Board approved cross-sectional study. The eligibility criteria were as follows: age > 60 years, no recent hospitalization within the past 12 months, no conditions that affect vitamin D status including vitamin D supplementation, and eGFR > 30 mL/min/1.73 m². Serum 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH) levels were assessed. Results: A total of 226 patients were enrolled. Data were expressed as mean ± SD. The mean serum 25(OH)D was 26.61 ± 10.44 ng/mL and the mean serum PTH was 50.67 ± 22.67 pg/mL. The prevalence of vitamin D deficiency [25(OH)D < 20 ng/mL] and secondary hyperparathyroidism [PTH > 65 pg/mL] were 25.3% and 18.1%, respectively. Patients with eGFR 30− < 60 mL/min/1.73m² had significantly higher prevalence of 25(OH)D < 20 ng/mL (33.7% versus 19.4%, p < 0.05) than patients with eGFR ≥ 60 mL/min/1.73 m². Multiple regression analysis showed independent negative association of serum PTH level with eGFR (mL/min/1.73 m², β: − 0.261, 95% CI [− 0.408, − 0.114]) and serum 25(OH)D (ng/mL, β: − 0.499, 95% CI [− 0.775, − 0.223], adjusted for possible confounders). Conclusions: The prevalence of vitamin D deficiency was higher in patients with eGFR 30 – < 60 mL/min/1.73 m² than those with eGFR ≥ 60 mL/min/1.73 m². Both decreased serum 25(OH)D levels and decreased eGFR were independently associated with increased serum PTH levels among these patients.