Hypomagnesemia: a potential underlooked cause of persistent vitamin D deficiency in chronic kidney disease

Association of serum magnesium levels with renal prognosis in patients with chronic kidney disease

BACKGROUND

Magnesium deficiency is associated with various health conditions, but its impact on the progression of chronic kidney disease (CKD) remains unclear. This study aimed to investigate the association between serum magnesium levels and prognosis of renal function in CKD patients.

METHODS

This is an analysis of the Japan Chronic Kidney Disease Database Ex　(J-CKD-DB-Ex), which is a multicenter prospective cohort including CKD patients enrolled from January 1, 2014 to December 31, 2020. We included adult outpatients with CKD stage G3 and G4 at the time of initial magnesium measurement. Patients were classified by magnesium levels as low (<1.7 mg/dl), normal (1.7-2.6 mg/dl), or high (>2.6 mg/dl). The primary outcomes were the composite of an eGFR < 15 ml/min/1.73 m2 or a ≥30% reduction in eGFR from the initial measurement, which was defined as CKD progression. We applied the Kaplan-Meier analysis and Cox regression hazard model to examine the association between magnesium levels and CKD progression.

RESULTS

The analysis included 9868 outpatients during the follow-up period. The low magnesium group was significantly more likely to reach CKD progression. Cox regression, adjusting for covariates and using the normal magnesium group as the reference, showed that the hazard ratio for the low magnesium group was 1.20 (1.08-1.34). High magnesium was not significantly associated with poor renal outcomes compared with normal magnesium.

CONCLUSION

Based on large real-world data, this study demonstrated that low magnesium levels are associated with poorer renal outcomes.

Biochemical Clusters as Substitutes of Bone Biopsies in Kidney Transplant Patients

Bone and mineral metabolism abnormalities are frequent in kidney transplant recipients and have been associated with cardiovascular morbidity. The primary aim of this study was to analyse the association between routine clinically available biochemical evaluation, non-routine histomorphometric bone evaluation, and vascular disease in kidney transplanted patients. A cross-sectional analysis was performed on 69 patients, 1-year after kidney transplantation. Laboratory analysis, radiography of hands and pelvis, bone biopsy, bone densitometry, and coronary CT were performed. One-year post-transplantation, nearly one-third of the patients presented with hypercalcemia, 16% had hypophosphatemia, 39.3% had iPTH levels > 150 pg/mL, 20.3% had BALP levels > 40 U/L, and 26.1% had hypovitaminosis D. Evaluation of extraosseous calcifications revealed low Adragão and Agatston scores. We divided patients into three clusters, according to laboratory results routinely used in clinical practice: hypercalcemia and hyperparathyroidism (Cluster1); hypercalcemia and high BALP levels (Cluster2); hypophosphatemia and vitamin D deficiency (Cluster 3). Patients in clusters 1 and 2 had higher cortical porosity (p = 0.001) and osteoid measurements, although there was no difference in the presence of abnormal mineralization, or low volume. Patients in cluster 2 had a higher BFR/BS (half of the patients in cluster 2 had high bone turnover), and most patients in cluster 1 had low or normal bone turnover. Cluster 3 has no differences in volume, or turnover, but 60% of the patients presented with pre-osteomalacia. All three clusters were associated with high vascular calcifications scores. Vascular calcifications scores were not related to higher bone mineral density. Instead, an association was found between a higher Adragão score and the presence of osteoporosis at the femoral neck (p = 0.008). In conclusion, inferring bone TMV by daily clinical biochemical analysis can be misleading, and bone biopsy is important for assessing both bone turnover and mineralization after kidney transplantation, although hypophosphatemia combined with vitamin D deficiency is associated with abnormal mineralization. The presence of hypercalcemia with high levels of PTH or high levels of BALP, or hypophosphatemia and vitamin D deficiency should remind us to screen vascular calcification status of patients.Clinical Research: ClinicalTrials.gov ID NCT02751099.