Prevalence and risk factors associated with persistent hyperparathyroidism in kidney transplant recipients

Abstract

Introduction: Secondary hyperparathyroidism (HPT) is a common complication of end-stage chronic kidney disease (CKD). Following kidney transplantation (KT), HPT typically resolves; however, it persists in 10 to 66% of patients one year post-KT, referred to as persistent hyperparathyroidism (HPTp), also known as tertiary HPT, increasing the risk of bone loss and fractures. Several factors may be associated with developing HPTp, but they have yet to be well-defined. Furthermore, there is no consensus on defining the PTHi levels to diagnose HPTp, with KDIGO guidelines recommending initiating treatment when PTHi is >100 pg/ml. Objectives: To assess the prevalence of HPTp in the first year post-KT and correlate it with serum calcium (Ca), phosphate (P), alkaline phosphatase (ALP), and renal function. Analyze the risk factors for HPTp development. Materials and Methods: An observational, longitudinal, and retrospective study was conducted on patients who received KT at the Nephrology Service of Córdoba Hospital between 2010 and 2019. We included 48 patients with an average age of 42.0 ± 11.8 years and 54% male; the patient's data were obtained from the service's medical records. Most patients received induction therapy with basiliximab and an immunosuppressive regimen comprising calcineurin inhibitors, mycophenolate, and steroids. The analyzed variables included recipient age, gender, donor type, CKD etiology, dialysis modality, and time on dialysis. PTHi, Ca, P, and ALP levels were recorded at the time of KT, at 6 and 12 months. Renal function was evaluated at one, six, and twelve months. Descriptive statistics were used for the analysis. Group comparisons were made using the Chi-square test and t-test, with p-values <0.05 considered significant. Results: The most prevalent CKD etiologies were nephropathies of unknown origin (31%) and nephroangiosclerosis (19%). Twenty-five patients had PTH levels exceeding 300 pg/ml before KT. Ten patients (20%), primarily women, presented HPTp one year post-KT. Longer time on dialysis (47.9 vs. 85.6 months; p < 0.01) and older recipient age (40.3 vs. 48.7 years; p < 0.003) were associated with the development of HPTp. Other risk factors for HPTp included higher levels of ALP and PTHi at six months post-KT. As expected, these patients tended towards hypercalcemia (10.5 vs. 9.6 mg/dl) and hypophosphatemia (2.5 vs. 3.5 mg/dl).

One year post-KT, renal function was similar in both groups, with 70% having a glomerular filtration rate between 30-60 ml/min and 30% >60 ml/min. Conclusion: The most significant risk factors for HPTp development post-KT were recipient age, time on dialysis, and levels of ALP and PTHi at six months post-KT. 80% of patients resolved HPT after one year of KT. Future strategies should focus on reducing waitlist time and timely management of tertiary HPT before transplantation.