Bone Material Strength Index Is Low in Patients With Cushing's Syndrome Even After Long-term Remission

Hypercortisolism in endogenous Cushing's syndrome (CS) results in decreased bone mineral density (BMD) and increased fracture risk. Although after remission BMD improves, the fracture rate remains elevated, suggesting that BMD may not adequately reflect fracture risk in this group. The aim was to evaluate bone material properties, another component of bone quality, using impact microindentation in patients with CS in remission.

Cross-sectional study in 60 CS patients and 60 age-, sex-, and BMD-matched controls at a tertiary referral center between 2019 and 2021. Bone material strength index (BMSi) was measured by impact microindentation using the OsteoProbe® device at the tibia. In addition, laboratory investigation, BMD, and vertebral fracture assessment were performed.

By design, patients and controls were comparable for age (median age 56.5 years), sex (48 women), and BMD at the lumbar spine and femoral neck. They were also comparable regarding the number of fragility fractures (21 vs 27, P = .22). The median time of remission in patients was 6 years (range 1 to 41). Despite comparable BMD, BMSi was significantly lower in CS patients compared to controls (76.2 ± 6.7 vs 80.5 ± 4.9, P < .001). In CS patients, BMSi was negatively correlated with body mass index (r = -0.354, P = .01) but not related to the presence of fracture, physiological hydrocortisone replacement use, other pituitary insufficiencies, or time since remission.

Bone material properties remain altered in patients with endogenous CS, even after long-term remission. These abnormalities, known to be associated with fractures in other populations, may play a role in the persistent bone fragility of steroid excess.