Association Between Serum Parathyroid Hormone Levels and Femoral Bone Mineral Density in Patients with Chronic Kidney Disease Stage 3.

Background: Chronic kidney disease (CKD) is associated with early disturbances in mineral metabolism that contribute to bone fragility. Secondary hyperparathyroidism is a key component of chronic kidney disease-mineral and bone disorder (CKD-MBD) and may affect bone even during the early stages of CKD. This study evaluated the association between serum parathyroid hormone (PTH) concentrations and bone mineral density (BMD) in patients with stage 3 CKD. Methods: A multicenter cross-sectional observational study was conducted in 203 patients with stage 3 CKD. Blood and 24 h urine samples were collected to measure creatinine, calcium, phosphate, magnesium, 25-hydroxyvitamin D, fibroblast growth factor 23 (FGF23), and PTH. Bone mineral density was assessed by dual-energy X-ray absorptiometry (DXA). Associations between serum PTH concentrations and BMD were analyzed. Results: Elevated serum PTH concentrations were associated with lower femoral BMD and less favorable femoral T-scores, whereas no significant associations were observed at the lumbar spine. Serum PTH concentrations were inversely correlated with femoral BMD and femoral T-scores. Patients with reduced femoral BMD also showed higher FGF23 concentrations and lower renal function, while serum calcium, phosphate, magnesium, and 25-hydroxyvitamin D concentrations did not differ significantly among the groups. Conclusions: Elevated serum PTH concentrations were associated with reduced femoral BMD in patients with stage 3 CKD, supporting preferential early involvement of cortical bone. Serum PTH may represent an accessible biomarker for the early identification of patients at increased risk of cortical bone loss before conventional biochemical abnormalities become clinically apparent.