SAT183 What Determines Bone Mineral Density Changes After Successful Parathyroidectomy In Primary Hyperparathyroidism?

Disclosure: J.E. Mosquera: None. X. Li: None. N. Maalouf: None. Background: Parathyroidectomy (PTX) is the only cure for primary hyperparathyroidism (PHPT). However, the impact of PTX on bone mineral density (BMD) is very variable. Methods: To assess the impact of demographic and clinical characteristics on BMD change post-PTX, we retrospectively reviewed charts of patients with biochemically proven PHPT and successful PTX between 2006 and 2022 at our institution and who had available pre- and post-PTX DXA scans. We extracted available demographic, clinical, and laboratory data including age, gender, race, body mass index, pre-PTX serum parathyroid hormone, calcium, phosphorus, alkaline phosphatase (Alkphos), 25-OH-vitamin D, and creatinine, 24-hour urine calcium, and use of bisphosphonates. The association between these parameters and BMD changes were assessed using univariate and multivariate models. Results: 121 patients (107 women) were included in this analysis. 35% were African American and 50% Hispanic. At PTX, mean (SD) age was 59 (12) years, BMI was 33 (7) kg/m(2). 36% had osteopenia and 47% had osteoporosis on pre-PTX DXA. 6% of patients used BP before PTX and 3% used BP within one year of PTX. At year 1 post-PTX, median BMD (25(th)-75(th) percentile) change was +2.7% (-0.2% - +6.6%) at the lumbar spine (LS), +2.4% (-0.5% - +5.9%) at the femoral neck (FN), +2.8% (0.7% - +4.7%) at total hip (TH), and +0.1% (-3.6% - +3.0%) at the 1/3 radius. In univariate analyses, 1-year change in FN BMD was positively associated with highest pre-PTX serum calcium, PTH, and Alkphos, and negatively associated with age and serum creatinine. TH BMD change at 1 year was positively associated with highest pre-PTX PTH and Alkphos, and negatively associated with lowest T-score at baseline, age, and pre-PTX serum phosphorus, 25-OH-D and creatinine. LS BMD change at 1 year was positively associated with highest pre-PTX serum calcium and PTH, and negatively associated with lowest phosphorus pre-PTX. In multivariate analyses, younger age, highest pre-PTX serum calcium, and lowest BMD T-score pre-PTX were all independently and significantly associated with greater increase in post-PTX BMD at the FN, TH, and LS. Moreover, pre-PTX Alkphos was associated with greater BMD gain at the FN and TH, while female gender was associated with greater gain in LS BMD. Conclusions: In patients with PHPT who undergo curative PTX, variable BMD changes are observed at 1-year post-PTX. Younger age at PTX, higher serum calcium, and lower BMD pre-PTX are all associated with greater BMD gains post-PTX. These findings should be considered in the counseling of PHPT patients undergoing PTX. Presentation: Saturday, June 17, 2023