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Background A 24-hour urine collection is routinely obtained in the workup of primary hyperparathyroidism (PHPT) to measure calcium and creatinine excretion, rule out familial hypocalciuric hypercalcemia, and guide diagnosis and management. Although hypercalciuria is expected and frequently observed in PHPT, hypocalciuria and/or a low urine calcium (uCa) to creatinine clearance ratio (UCCCR) may occur. Variables including race, age, renal function, and 25-OH vitamin D levels can affect urinary calcium excretion. Given the utility of obtaining urine calcium excretion in patients with PHPT, we performed a retrospective analysis on patients with PHPT to evaluate the effect of clinical variables on urinary calcium excretion, and to test the hypothesis that hypocalciuria may delay parathyroidectomy in PHPT. Methods We retrospectively reviewed charts of patients with PHPT with available 24-hour uCa who underwent successful parathyroidectomy at our institution between 2009 and 2021. We extracted available demographic, clinical, and laboratory data including first available uCa and creatinine excretion prior to parathyroidectomy, age, gender, ethnicity, BMI, eGFR, serum calcium, phosphorus, PTH, 25-hydroxyvitamin D, and 24-hour sodium excretion. The association between these parameters and uCa and UCCR was assessed in univariate and multivariate models. We compared characteristics of PHPT patients with vs. without hypocalciuria, and duration between uCa measurement and parathyroidectomy. Results 643 PHPT patients were included in this analysis. 8.4% of patients had a 24-hr uCa excretion rate below 100mg/day, and 18.7% had a UCCR<1%.Compared to PHPT patients with UCCCR≥1%, those with UCCCR<1% had a significantly higher proportion of African Americans (22.2% vs 9.1%; p=0.0029), a lower mean serum calcium (p=0.0027), and 25-hydroxyvitamin D (p=0.035). In multivariate analysis, gender, race, serum calcium, serum 25-OH-vitamin D, and 24-hour urine sodium were all significant predictors of UCCCR. The UCCCR<1% group had a significantly longer median time from uCa measurement to parathyroidectomy [8.4 (Interquartile range IQR: 3.3-29.4) vs. 4.2 (IQR: 2.4-8.7) months, p<0.001).Compared to PHPT patients with 24-hr uCa≥100 mg/day, those with 24-hr uCa<100 mg/day had significantly lower mean serum calcium (p=0.002), eGFR (p<0.0001), urine sodium excretion (p=0.036), and significantly greater serum phosphorus (p=0.0085) and PTH (0.0078). In multivariate analysis, race, BMI, serum calcium, eGFR and urine sodium were all significant predictors of 24-hr uCa. The uCa<100 mg/day group had a significantly longer median time from uCa measurement to parathyroidectomy [9.7 (IQR: 3.3-32.2) vs. 4.2 (IQR: 2.4-8.8) months, p<0.001). Conclusions Although elevated uCa is used as a diagnostic marker and indication for parathyroidectomy in PHPT, hypocalciuria and UCCCR<1% are relatively common in PHPT patients, and associated with a significant delay in parathyroidectomy. Intrinsic (race, gender) and extrinsic (vitamin D status, renal function, sodium intake/excretion) factors are all determinants of calcium excretion in PHPT. Presentation: Monday, June 13, 2022 12:00 p.m. - 12:15 p.m.

Background Low bone mineral density (BMD) is more prevalent in people living with HIV (PLWH) than in the general population. Although no consensus exists regarding when to start screening for BMD loss in PLWH, the Infectious Diseases Society of America (IDSA) recommends dual x-ray absorptiometry (DXA) for men aged ≥50 years, postmenopausal women, and patients with a history of fragility fracture, chronic glucocorticoid treatment, or at high fall risk. The objective of this study is to evaluate how well this guideline is being carried out in a population of veterans living with HIV (VLWH). Methods We retrospectively identified VLWH seen at the Veterans Affairs Medical Center (VAMC) in Houston, TX, between 2014–2018 via the VAMC HIV Registry. We extracted demographic, laboratory, and clinical variables, as well as DXA results via this registry database and subsequent chart review. Results We identified 1,306 VLWH who received care between 2014–2018; 197 turned 50 years old during this time period. Of those, only 32 (16.2%) underwent DXA (2 women, 30 men). DXA revealed normal BMD in 17 (53.1%), osteopenia in 12 (37.5%), and osteoporosis in 3 (9.4%), as defined by traditional DXA T-score cutoffs. Average CD4 count at time of DXA was 698 cells/mm3 (n=30) (average CD4 for those with normal DXA was 654 [n=16] and for those with osteopenia/osteoporosis it was 749 [n=14]; t-test p = 0.47). Thirty had HIV viral load (VL) < 100 copies/mL; the remaining 2 had VLs of 11,200 and 2,980, both with normal DXAs. Vitamin D (VD) levels were available for 1,005 (77%) VLWH in the study cohort. Of those, 278 (27.7%) were VD deficient (25-hydroxy VD level of < 20 ng/mL). VD levels were available for 31 of the 32 VLWH who had DXA after turning 50 years old; the average VD level was 22.76 (24.61 [n=16] for those with normal BMD and 20.78 [n=15] for those with osteoporosis/osteopenia; t-test p = 0.30). Conclusion Our results indicate that adherence to IDSA BMD screening guidelines in VLWH can be improved. Given that nearly half of the screened patients showed evidence of BMD loss on their initial DXA, efforts should be made to increase awareness and screening in this vulnerable population. Prevention, earlier diagnosis, and treatment of BMD loss in VLWH would likely lead to decreased morbidity associated with fractures due to low BMD in this population. Disclosures All Authors: No reported disclosures

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