Parathyroidectomy improves hypercalciuria in patients with primary hyperparathyroidism.

BACKGROUND: Hypercalciuria is an important manifestation of primary hyperparathyroidism and may contribute to the risk of nephrolithiasis. This study examined the impact of parathyroidectomy on 24-hour urinary calcium (24-hour UCa ) levels and rates of resolution of hypercalciuria after surgery.

METHODS: A retrospective cohort study was performed of patients who underwent curative parathyroidectomy for primary hyperparathyroidism from 2007 to 2017. Baseline and postoperative urine and serum biochemistry levels were analyzed. The relationship between preoperative 24-hour UCa levels and the absolute decrease in postoperative UCa excretion was assessed using Spearman's rank correlation coefficient.

RESULTS: Of 110 patients, 84 (76.4%) experienced a ≥20% decrease in 24-hour UCa level postoperatively. These patients had a higher baseline median 24-hour UCa level (293.5 vs 220.5 mg/24-hour; P = .001), higher baseline mean serum parathyroid hormone (106.5 vs 83; P = .05) and were more likely to have single gland disease (85.7% vs 65.4%, P = .04) compared with patients in whom 24-hour UCa excretion did not improve. Of the 28 patients (25%) who were hypercalciuric (24-hour UCa >400 mg/day) at baseline, 22 (79%) became normocalciuric postoperatively. A linear correlation was observed between preoperative 24-hour UCa levels and the decline in 24-hour UCa excretion after surgery (R2  = 0.59, P < .0001) such that the degree of improvement could be predicted using the following equation: absolute decrease in postoperative 24-hour UCa  = 0.68 × preoperative 24-hour UCa -68.

CONCLUSION: Parathyroidectomy reduces 24-hour UCa excretion in the majority of patients with PHPT and restores normocalciuria in 79% of patients with hypercalciuria at baseline.