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

CONTEXT: 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.

OBJECTIVES: To determine the prevalence and predictors for renal abnormalities (nephrocalcinosis and decreased estimated glomerular filtration rate [eGFR]) in children with treated hypoparathyroidism.

DESIGN AND SETTING: A retrospective chart review of patients with permanent hypoparathyroidism at the Hospital for Sick Children, Toronto, between 1996 and 2013.

PATIENTS: 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.

MAIN OUTCOME MEASURES: The presence or absence of nephrocalcinosis as detected on ultrasound and eGFR were evaluated.

RESULTS: 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.

CONCLUSIONS: 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.