Evaluation of bone-related mechanical properties in female patients with long-term remission of Cushing's syndrome using QCT-based Finite Element analysis.

BACKGROUND:Hypercortisolism in Cushing's syndrome (CS) is associated with bone loss, skeletal fragility and altered bone quality. No studies evaluated bone geometric and strain-stress values in CS patients after remission thus far. PATIENTS AND METHODS:Thirty-two women with CS in remission [mean age (±SD) 51 ± 11; BMI, 27 ± 4 Kg/m2; mean time of remission, 120 ± 90 months] and 32 age-, BMI- and gonadal status-matched female controls. Quantitative computed tomography (QCT) was used to assess volumetric bone mineral density (vBMD) and buckling ratio, cross sectional area and average cortical thickness at the level of the proximal femur. Finite Element (FE) models were generated from QCT to calculate strain and stress values [Maximum Principal Strain (MPE), maximum Strain Energy Density (SED), maximum Von Mises (VM) and Maximum Principal Stress (MPS)]. Areal BMD (aBMD) and trabecular bone score (TBS) were assessed by dual-energy x-ray absorptiometry (2D DXA). RESULTS:Trabecular vBMD at total hip and trochanter were lower in CS as compared with controls (p < 0.05). Average cortical thickness was lower and buckling ratio was greater in CS vs. controls (p < 0.01). All strain and stress values were higher in CS patients vs. controls (p < 0.05). 2D DXA-derived measures were similar between patients and controls (p > 0.05). Prior hypercortisolism predicted both VM (β 0.30, p = 0.014) and MPS (β 0.30, p = 0.015), after adjusting for age, BMI, menopause, delay to diagnosis and duration of remission. CONCLUSIONS:Women with prior hypercortisolism have reduced trabecular vBMD and impaired bone geometrical and mechanical properties, which may contribute to an elevated fracture risk despite long-term remission.