Increased Skeletal Parathyroid Hormone Responsiveness and Risk of Decreased Lumbar Bone Mineral Density in Patients Receiving Chronic Hemodialysis: A 5‐Year, Retrospective, Longitudinal Study

BACKGROUND: Parathyroid hormone (PTH) stimulates bone resorption, causing fractures. Skeletal PTH responsiveness varies widely among patients undergoing hemodialysis (HD). We examined whether skeletal PTH responsiveness can be a determining and/or dynamic factor of bone mineral density (BMD) in patients undergoing chronic HD. METHODS: We conducted a 5-year retrospective longitudinal study among patients undergoing chronic HD between 2018 and 2023. The tartrate-resistant acid phosphatase-5b (TRACP-5b)/intact PTH (iPTH) ratio was used as an index of skeletal PTH responsiveness. The relationship between the TRACP-5b/iPTH ratio and BMD in 2018, and the relationship between changes (Δ) in the TRACP-5b/iPTH ratio and BMD over 5 years were investigated. Furthermore, in the linear regression analyses for ΔBMD, we used the median values of every 3-month data over a 5-year period to minimize the influence of short-term fluctuations in concentrations. Statistical significance was set at p < 0.05. RESULTS: The TRACP-5b/iPTH ratio and BMD at the lumbar spine (LS) and femoral neck (FN) in 2018 were not inversely correlated. However, the relationship between the ΔTRACP-5b/iPTH ratio and ΔLS-BMD in the 5-year period was significantly inversely correlated. Significant variables in the single regression analyses for ΔBMD were adjusted for age, sex, body mass index, or serum albumin concentration, and multiple regression analyses were performed with two variables, including each adjusted variable. Only the ΔTRACP-5b/iPTH ratio showed a significant inverse correlation with ΔLS-BMD in all models, not with ΔFN-BMD in any models. CONCLUSIONS: A long-term increase in skeletal PTH responsiveness is associated with a greater reduction in LS-BMD in patients undergoing chronic HD.