#1692 Prevalence and risk factors for persistent hyperparathyroidism in long-term kidney transplant recipients

Abstract Background and Aims Secondary hyperparathyroidism, associated with fractures and cardiovascular mortality in end-stage kidney disease, often resolves after kidney transplantation (KT). However, limited knowledge exists regarding persistent hyperparathyroidism (persist-PTH) after long-term KT. We aimed to define the prevalence and risk factors of persist-PTH in KT recipients at ≥3 years post-KT. Method A historical cohort study was conducted in adult KT recipients at Srinagarind Hospital, Khon Kaen University, Thailand, from 2015 to 2020. Persist-PTH is defined as serum parathyroid hormone (PTH) exceeding twice the upper limit of normal (130 pg/mL) after ≥3 years post-KT. Results A total of 281 patients were included, with a median age of 41.4 years (interquartile range (IQR), 32.7-49.1), and 117 patients (41.6%) were female. The median post-KT follow-up was 71 months (IQR, 54-89) with a glomerular filtration rate (GFR) of 61.8 mL/min/1.73 m² (IQR, 48.2-76.9). The respective median pre-KT and post-KT PTH were 403 pg/mL (IQR, 196.3-862) and 96.7 pg/mL (IQR, 67.3-166). Post-KT PTH levels correlated with pre-KT PTH levels (r²=0.18; P0.001). Persist-PTH occurred in 100 patients, with a prevalence of 35.6% (95% confidence interval (CI), 30.2-41.4%). Multivariate analysis revealed significant associations between persist-PTH and a longer dialysis vintage (odds ratio (OR) 1.13 per 6-month increase; 95% CI, 1.06-1.20; P0.001), lower GFR (OR, 0.76 per 10 mL/min/1.73 m² increase; 95% CI, 0.63-0.92; P=0.004), and higher pre-KT PTH (HR, 1.06 per 50 pg/mL increase; 95% CI, 1.02-1.10; P=0.001). Furthermore, persist-PTH with hypercalcemia (10.2 mg/dL) occurred in 44 patients (15.7%; 95% CI, 11.8-20.4%), and with hypophosphatemia (2.5 mg/dL) in 23 patients (8.2%; 95% CI, 5.5-12.0%). Conclusion Persist-PTH occurred in over one-third of long-term post-KT recipients, particularly in those with extended dialysis vintage, impaired graft function, and elevated pre-KT PTH levels. This underscores the need for optimal pre-KT PTH control and vigilant graft function monitoring to prevent persist-PTH.