Persistent Hyperparathyroidism after Pediatric Kidney Transplantation Da Hyun Kim, Joo Hoon Lee, Young Seo Park Department of Pediatrics, Asan Medical Center Children’s Hospital, University of Ulsan College of Medicine, Seoul, Korea Purpose : Hyperparathyroidism(HPT) is a common consequence of end stage renal disease(ESRD). Most patients who undergo kidney transplantation(KT) have parathyroid hormone( PTH) levels corrected over time, but some patients still have persistent HPT. The purpose of this study was to investigate PTH levels in children after KT and the risk factors of persistent hyperparathyroidism after KT. Methods : We retrospectively reviewed the data of children under 18 years of age who underwent KT from 1992 to 2017 at Asan Medical Center Children’s Hospital and excluded patients whose glomerular filtration rates were below 60 ml/min/ 1,73 m2. A total of 56 patients were enrolled in this study. Mean follow-up period after KT was 12.2 years (range= 1-25.4years) Persistent HPT is defined as HPT after I year of KT in patients with stable renal function. Pretransplant PTH level, pretransplant calcium phosphate products, ESRD period ,etiology of ESRD, and other factors were compared between the patients with persistent HPT and without persistent HPT. Results : Among 56 patients, there were 34(60.7%) without persistent HPT and 22(39.3%) with persistent HPT. In patient without persistent HPT, normalized period of PTH was 3.8±3.7mo after KT., and this period was inversely correlated with the ESRD period. Pretransplant PTH level was significantly high in the persistent HPT group( 653.0±478.2 vs 364.4±285.8 , P=0.036). Other possible risk factors such as ESRD period and pretransplant calcium phosphate products were not significantly different between the two groups. There was no statistically significant difference between the two groups in terms of the ratio of male, age of transplantation and etiology of ESRD. Conclusion : PTH after KT were more rapidly normalized in patients with shorter duration of ESRD. Pretransplant PTH level is the risk factor of persistent HPT after KT. It is important to control pretransplant PTH to prevent persistent HPT.