24-Hour urinary calcium in primary hyperparathyroidism

Objective: To establish whether urinary and serum calcium levels are correlated in patients with primary hyperparathyroidism (PHPT) and to evaluate related factors including serum levels of parathyroid hormone (PTH) and vitamin D, age, gender and renal function. Design: Retrospective review on patients undergoing a parathyroidectomy for PHPT from 2000- 2008. Data collected included: age, sex, preoperative serum calcium (ionized and total), creatinine, PTH, postoperative ionized calcium, vitamin D, and 24-hour urine calcium and creatinine. Data were evaluated by standard descriptive statistics. Results: Of the 214 patients evaluated, preoperative 24-hour urinary calcium was available for 150 patients (70%). 24-hour urine calcium levels did not correlate significantly with preoperative total serum or ionized calcium, PTH, vitamin D, or postoperative serum ionized calcium. There were significant correlations (P < 0.0001) of 24-hour urinary calcium with age, serum creatinine, and urine creatinine. Secondary analysis grouped subjects by urinary calcium level greater or less than 400 mg/24 hours. Age and urinary creatinine were significantly different between the two groups. Conclusions: In patients with PHPT who underwent parathyroidectomy, there was little correlation between preoperative 24-hour urine calcium and preoperative serum calcium, PTH, or vitamin D levels. 24-hour urine calcium levels were correlated with renal function and age, but these correlations are likely to occur in the general population and are not specific to this disease group.