Vitamin D Status and Proteinuria Severity in Children with Steroid-Sensitive and Steroid-Resistant Nephrotic Syndrome

Abstract

Introduction: Vitamin D deficiency is a common metabolic abnormality in children with nephrotic syndrome (NS), primarily caused by urinary loss of vitamin D–binding protein (VDBP). The severity of deficiency may differ depending on steroid responsiveness, with steroid-resistant nephrotic syndrome (SRNS) patients showing more prolonged proteinuria compared to steroid-sensitive nephrotic syndrome (SSNS).

Objective: To compare serum vitamin D levels and proteinuria severity between patients with SRNS and SSNS.

Methods: A cross-sectional study was conducted at Dr. Wahidin Sudirohusodo Hospital, Indonesia, from January to March 2025, involving 36 children aged 1–18 years diagnosed with NS (18 SRNS and 18 SSNS). Serum vitamin D levels were measured, and urinary protein was assessed using a semi-quantitative dipstick and protein–creatinine ratio (PCR). Data were analyzed using appropriate statistical tests to compare vitamin D and proteinuria severity between groups.

Results: Serum vitamin D levels were significantly lower in SRNS compared to SSNS (p = 0.033), and all SRNS patients were vitamin D deficient. Almost all SRNS patients (94.4%) had urine PCR ≥ 0.50 g/g, compared to 77.8% in SSNS (p = 0.148). Semi-quantitative analysis showed that heavy proteinuria (4+) was more common in SRNS (61.1%) than in SSNS (38.9%) (p = 0.478). Among SRNS children, those with nephrotic-range proteinuria had markedly lower vitamin D levels than those with non-nephrotic proteinuria (p = 0.005).

Conclusion: Children with SRNS exhibit significantly lower serum vitamin D levels and more severe proteinuria than those with SSNS. Persistent nephrotic-range proteinuria is strongly associated with reduced vitamin D levels. Routine monitoring and appropriate vitamin D supplementation are recommended, particularly for SRNS patients.