RF18 | PMON103 Hypercalciuria in Young Adults With Primary Hyperparathyroidism Is Less Likely to Resolve After a Successful Parathyroidectomy Compare to Older Adults

INTRODUCTION: Hypercalciuria is one of the reported complications in patients with primary hyperparathyroidism (PHPT). Profound hypercalciuria in the settings of renal stones is considered to be one of the indications for parathyroidectomy. However, limited data is available to describe the rate of hypercalciuria resolution following successful parathyroidectomy in patients with PHPT who had elevated pre-op 24 hour urine calcium levels. OBJECTIVE: To describe efficacy of successful parathyroidectomy (defined as normalization of serum calcium) in patients with primary hyperparathyroidism and hypercalciuria (defined as 24 hour urine calcium > 250 mg/24 hr) on resolution of hypercalciuria (defined as 24 hour urine calcium < 200 mg/24hr). Design: This is a retrospective study in which 51 eligible patients (with parathyroidectomies performed from August 2015 to June 2021) were chart reviewed. Twenty nine patients with complete records pre and post parathyroidectomy were included in the analysis. Setting: Single outpatient endocrinology center in Las Vegas, Nevada. Participants: A population of 29 adults aged 29 to 72 years with confirmed primary hyperparathyroidism and hypercalciuria who had a complete resolution of hypercalcemia status post parathyroidectomy. Main outcome measure: Resolution of hypercalciuria. RESULTS: 12 patients (41%) had complete resolution of hypercalciuria after parathyroidectomy. The mean age among patients with resolution was 61.4 years (SD 6.7 years) at the time of surgery vs. 50.5 (SD 11.9 years) among not responders (p= 0.008). There was no significant difference between the resolved and not resolved groups with regard to sex, history of renal stones, history of osteoporosis, location of parathyroid adenoma, pre-op PTH, calcium, and 24 hour urine calcium (p >0.05). Nephrolithiasis occured in 34% of cases. Osteoporosis occurred in 24% of cases. Average pre-op 24 hour urine calcium was 427 mg/24hr (SD 134 mg/24hr, collected on average at 5 months pre-op). Average post-op 24 hour urine calcium was 204 mg/24hr (SD 83 mg/24hr, collected on average at 22 months post-op). In a multivariate analysis, for each year of age (at the time of surgery) increase, the odds of resolution of hypercalciuria increased by 37% (p= 0.036, 95% CI [1.020-1.840]; stepwise logistic regression). For each 1 mg increase in pre-op urine calcium odds of resolution of hypercalciuria decreased by 1.7% after successful parathyroidectomy (p=0.033, 95% CI [0.967, 0.999]). CONCLUSIONS: These results suggest that hypercalciuria is less likely to resolve in younger patients with PHPT after successful parathyroidectomy compared to older adults. Our data also suggests that resolution of hypercalciuria in primary hypercalciuria is inversely related to the pre-op 24 hour urine calcium levels (the higher the pre-op 24 hour urine calcium level, the less likely the hypercalciuria to resolve after successful parathyroidectomy). Presentation: Sunday, June 12, 2022 1:12 p.m. - 1:17 p.m., Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.