#1706801 Impact of Adrenalectomy on Bone Density and Quality in Patients with Mild Autonomous Cortisol Secretion: A Prospective Longitudinal Cohort Study

Patients with mild autonomous cortisol secretion (MACS) have a high risk of fractures, discordant to the degree of bone mineral density (BMD) loss. Increased risk of fractures may be due to impaired bone quality. Previous cross-sectional studies demonstrated that trabecular bone score (TBS), a DXA-based measurement that correlates with parameters of bone microstructure, was lower in MACS vs referent subjects. The impact of adrenalectomy on TBS has not been characterized in patients with MACS. Thus, we aimed to determine the impact of adrenalectomy in patients with MACS on TBS and BMD. In this single-center prospective cohort study, adults with MACS scheduled for adrenalectomy and referent subjects were enrolled between 2018 and 2023. MACS was defined as cortisol >1.8 mcg/dL after 1 mg dexamethasone suppression test without features of overt hypercortisolism. Referent subjects were included if they had no adrenal disorders. Participants underwent a bone density scan with TBS at baseline and a follow-up evaluation at least 10 months later. Differences were assessed for (1) femur neck BMD (2) total femur BMD (3) forearm radius 1/3 BMD (4) spine L1-L4 BMD (5) spine L1-L4 TBS. We evaluated 41 patients before and after adrenalectomy, and 31 referent subjects at baseline and follow-up visit, at a similar interval (median 1.6, IQR 1.2-2.0 vs 1.5, IQR 1.0-2.2 years, P=0.759). Both groups had similar sex distributions (women, 66% vs 84%, P=0.086), however, patients with MACS were older than the referent group (median age 57.3, IQR 48.8-66.9 vs 49.0, IQR 41.7-57.9 years, P=0.005). After adrenalectomy, patients demonstrated no change in femur neck BMD (mean change -0.009 g/cm, SD: 0.04, P=0.198), total femur BMD (mean change -0.013, SD: 0.04, P= 0.078), or spine BMD (mean change -0.016 g/cm, SD=0.06, P=0.09). Radius BMD deteriorated in both patients (mean change -0.034, SD=0.045, P< 0.001) and referent subjects (mean change -0.018, P=0.002). TBS improved in patients after adrenalectomy by a mean of 0.037 g/cm, SD 0.085, P=0.032, while TBS in referent subjects did not change (mean change -0.004, SD=0.051, P=0.539). Adrenalectomy leads to improvement in bone quality, but not density in patients with MACS.