Serum Magnesium and Bone Health in Pediatric Nephrotic Syndrome: A Cross-Sectional Study From South Asia.

Background Metabolic bone disease (MBD) is common in pediatric nephrotic syndrome (NS), yet magnesium (Mg)-a co-factor for vitamin D metabolism and parathyroid hormone (PTH) secretion-has been under-studied. Objective To evaluate serum Mg status in children with NS and its relationship with bone health and mineral metabolism. Methods We conducted a cross-sectional study of consecutively enrolled children with NS (N=370) at a tertiary center. Demographics, NS phenotype, treatment exposure, dual-energy X-ray absorptiometry (DEXA)-based bone density, and laboratory parameters-including Mg, calcium, phosphorus, alkaline phosphatase (ALP), 25-hydroxyvitamin D [25(OH)D], and intact PTH-were recorded. Associations between Mg and clinical/laboratory variables were assessed using t-tests/ analysis of variance (ANOVA), Pearson correlations, and multivariable models. Results A total of 370 pediatric patients with NS were included (mean age: 6.02 ± 3.3 years; 263 males, 71.1%). NS phenotypes included: steroid-resistant NS (SRNS, n=47, 12.7%), frequently relapsing NS (FRNS, n=173, 46.8%), steroid-dependent NS (SDNS, n=82, 22.2%), and infrequent relapsers NS (IFRNS, n=62, 16.8%). The mean serum magnesium (sMg) level was 1.73 ± 0.42 mg/dL (range: 0.8-2.9 mg/dL). Children with SRNS had significantly lower sMg levels compared to steroid-sensitive NS (SSNS) (1.35±0.36 vs. 1.75±0.42 mg/dL; p=0.002). No significant associations were found between sMg and demographic or clinical variables (all p>0.05). The sMg showed a negative correlation with PTH levels (r=-0.118; p=0.027) but no significant correlation with serum calcium, phosphorus, ALP, or 25(OH)D levels. Conclusions Lower Mg is associated with higher PTH and reduced bone density in pediatric NS, independent of high rates of vitamin D deficiency. Routine Mg assessment may help risk-stratify bone health and represents a modifiable target for future trials.