The Impact of Hypoparathyroidism Treatment on the Kidney in Children: Long-Term Retrospective Follow-Up Study.

Adults with hypoparathyroidism have significant rates of nephrocalcinosis and impaired renal function. Little is known about the impact of hypoparathyroidism treatment on renal function in children. To determine the prevalence and predictors for renal abnormalities (nephrocalcinosis and decreased estimated glomerular filtration rate [eGFR]) in children with treated hypoparathyroidism. A retrospective chart review of patients with permanent hypoparathyroidism at the Hospital for Sick Children, Toronto, between 1996 and 2013. Data of 29 patients (15 males) followed for at least 1 year with documented hypoparathyroidism were analyzed. Mean duration of follow up was 7.4 ± 5 years. The presence or absence of nephrocalcinosis as detected on ultrasound and eGFR were evaluated. Time-weighted average serum measurements were calculated for all biochemical variables. Mean total and ionized serum calcium were 8.9 ± 0.8 and 4.6 ± 0.5 mg/dL, respectively. Nephrocalcinosis was observed in 38% of the subjects, with the most significant predictors being the degree of relative hypercalcemia and hyperphosphatemia (R(2) = 0.47, P < .01). Although all patients had an eGFR greater than 60, in 45% of the children, the eGRF was between 60 and 90 mL/min per 1.73 m(2). Higher calcium concentrations (r = -0.42, P = .02) and a greater proportion of time with relative hypercalcemia (r = -0.41, P = .03) were associated with lower eGFR. Our results establish that children with hypoparathyroidism treated with calcitriol and calcium supplements are at risk for nephrocalcinosis and decreased eGFR. Because hypoparathyroidism is most commonly a life-long condition, careful monitoring and management of calcium abnormalities has important future implications.