Bone quality, as measured by trabecular bone score in patients with adrenal incidentalomas with and without subclinical hypercortisolism

摘要

Patients with adrenal incidentalomas (AIs) and subclinical hypercortisolism (SH) have increased risk of fracture independent of bone mineral density (BMD) and possibly due to reduced bone quality. The trabecular bone score (TBS) has been proposed as a index of bone microarchitecture. The aim of the study was to investigate TBS in AI. In 102 AI patients, SH was diagnosed in the presence of at least two of the following: (1) urinary free cortisol >70 μg/24 h (193.1 nmol/L); (2) cortisol after 1-mg dexamethasone suppression test (1-mg DST) >3.0 μg/dL (82.8 nmol/L); or (3) adrenocorticotropic hormone (ACTH) <10 pg/mL (<2.2 pmol/L). In patients and in 70 matched controls, BMD was measured at lumbar spine (LS) and femur (neck [FN] and total [FT]) by dual X-ray absorptiometry and TBS was assessed in the region of LS-BMD; BMD and TBS data were reported as Z-scores. In patients, vertebral deformities were assessed by radiograph. Patients with SH (n = 34) had lower LS-BMD (-0.31 ± 1.17), FT-BMD (-0.29 ± 0.91), and TBS (-3.18 ± 1.21) than patients without SH (n = 68, 0.31 ± 1.42, p = 0.03; 0.19 ± 0.97, p = 0.01; -1.70 ± 1.54, p < 0.0001, respectively) and controls (0.42 ± 1.52, p = 0.02; 0.14 ± 0.76, p = 0.02; -1.19 ± 0.99, p < 0.0001, respectively). TBS was inversely correlated with 1-mg DST (β = -0.26, t = -2.79, p = 0.006) regardless of age, LS-BMD, body mass index (BMI), and gender. The presence of fracture was associated with low TBS alone (odds ratio [OR], 4.8; 95% confidence interval [CI], 1.85-12.42, p = 0.001) and with the cluster low TBS plus low LS-BMD (OR, 4.37; 95% CI, 1.71-11.4, p = 0.002), after adjustment for age, BMI, and gender. Low TBS plus low LS-BMD showed a good specificity (79%) for predicting fractures, whereas normal TBS (ie, > -1.5) plus normal LS-BMD high specificity (88.1%) for excluding fractures. Finally, TBS predicted the occurrence of a new fracture in 40 patients followed for 24 months (OR, 11.2; 95%CI, 1.71-71.41, p = 0.012) regardless of LS-BMD, BMI, and age. In SH, bone quality, as measured by TBS, is altered. TBS is useful in detecting AI patients at risk of fractures.