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

The prevalence of hypercalciuria before and after surgery was 74% and 32%, respectively. Before, surgery patients with cRL showed lower calcium and higher phosphate levels than those without cRL (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, and PTH levels were comparable between patients with and without cRL. The prevalence of the histological finding of parathyroid hyperplasia was higher in patients with cRL (50%) than in patients without cRL (22%) (P = .01). The presence of cRL was independently associated with presurgery hypercalciuria (odds ratio, 4.71; 95% confidence interval, 1.18-18.8; P = .03) and parathyroid hyperplasia (odds ratio, 3.52; 95% confidence interval, 1.31-9.43; P = .01). Only patients without cRL had improved BMD at the spine (P = .04), total femur (P = .01), and femoral neck (P = .01).

CONCLUSIONS

cRL is present in 30% 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.