Hypercalciuria may persist after successful parathyroid surgery and it is associated with parathyroid hyperplasia

Context: Hypercalciuria is frequently found in primary hyperparathyroidism (1HPT) and, although it generally normalizes after successful parathyroidectomy, may persist in some patients. The factors associated with persistent calcium renal leak (cRL) have not been clarified. Objective: The purpose of this study was to determine the prevalence of cRL in our 1HPT population and investigate cRL-related factors. Design: This was a retrospective longitudinal study. Setting: The study was conducted in an outpatient setting. Patients/Intervention: The participants were 95 patients with 1HPT successfully operated on who had a normal estimated glomerular filtration rate. Main Outcome Measures: The biochemical parameters of calcium metabolism and bone mineral density (BMD) measured by dual-X-ray absorptiometry before and 24 months after surgery were assessed. All histological findings were recorded. Results: Theprevalence of hypercalciuria beforeandafter surgerywas74%and32%,respectively. Before, surgerypatientswithcRLshowedlowercalciumandhigherphosphatelevelsthanthosewithoutcRL(10.9± 0.6 vs 11.4±0.8 mg/dL [2.7±0.2 vs 2.8±0.2 mmol/L], P<01 and 2.6±0.5 vs 2.4±0.4 mg/dL [0.84±0.2 vs 0.77±0.1 mmol/L], P=.04, respectively), whereas 24-h calciuria levels and the prevalence of 1HPT complications (osteoporosis, renal stones, and hypertension) were comparable. After surgery, serum calcium, phosphate,andPTHlevelswerecomparablebetweenpatientswithandwithoutcRL.Theprevalence ofthehistological findingofparathyroidhyperplasiawashigherin patientswithcRL(50%)thanin patients without cRL (22%) (P<01). The presence of cRL was independently associated with presurgery hypercalciuria( oddsratio,4.71;95%confidenceinterval,1.18-18.8;P<03)andparathyroidhyperplasia(oddsratio, 3.52;95%confidenceinterval,1.31-9.43;P<01).OnlypatientswithoutcRLhadimprovedBMDatthespine (P<04), total femur (P<01), and femoral neck (P<01). Conclusions: cRL is present in30%of patients with 1HPT after successful surgery, and it is associated with parathyroid hyperplasia before surgery and the lack of improvement in BMD after surgery.