A Prospective Cohort Study of Mineral Metabolism After Kidney Transplantation

Background Kidney transplantation corrects or improves many complications of chronic kidney disease, but its impact on disordered mineral metabolism is incompletely understood. Methods We performed a multicenter, prospective, observational cohort study of 246 kidney transplant recipients in the United States to investigate the evolution of mineral metabolism from pretransplant through the first year after transplantation. Participants were enrolled into 2 strata defined by their pretransplant levels of parathyroid hormone (PTH), low PTH (>65 to 300 pg/mL; n = 112), and high PTH (>300 pg/mL; n = 134) and underwent repeated, longitudinal testing for mineral metabolites. Results The prevalence of posttransplant, persistent hyperparathyroidism (PTH >65 pg/mL) was 89.5%, 86.8%, 83.1%, and 86.2%, at months 3, 6, 9, and 12, respectively, among participants who remained untreated with cinacalcet, vitamin D sterols, or parathyroidectomy. The results did not differ across the low and high PTH strata, and rates of persistent hyperparathyroidism remained higher than 40% when defined using a higher PTH threshold greater than 130 pg/mL. Rates of hypercalcemia peaked at 48% at week 8 in the high PTH stratum and then steadily decreased through month 12. Rates of hypophosphatemia (<2.5 mg/dL) peaked at week 2 and then progressively decreased through month 12. Levels of intact fibroblast growth factor 23 decreased rapidly during the first 3 months after transplantation in both PTH strata and remained less than 40 pg/mL thereafter. Conclusions Persistent hyperparathyroidism is common after kidney transplantation. Further studies should determine if persistent hyperparathyroidism or its treatment influences long-term posttransplantation clinical outcomes.