Context. In patients with adrenal incidentalomas and subclinical hypercortisolism (SH), the factors influencing bone and the prevalence of vertebral fractures are debated. Spinal deformity index (SDI), which reflects bone quality, has never been evaluated.

Objective. To investigate in these patients SDI and factors influencing the prevalence of fractures.

Design. Retrospective, multicenter.

Setting. In- and out-patient basis.

Patients. 287 AI patients (111 eugonadal males, 31 pre-menopausal, 145 post-menopausal females) and 194 controls (90 eugonadal males, 29 pre-menopausal, 75 post-menopausal females).

Main Outcome Measure. Bone mineral density (BMD) was measured by Dual X-ray Absorptiometry at spine (LS) and femur (FN). By radiograph each vertebra was assessed as intact (grade 0) or grade 1 (20–25%), 2 (25–40%), or 3 (>40%) deformity; SDI was calculated by summing the grade of deformity for each vertebra. SH was diagnosed in the presence of at least 2 out of: urinary free cortisol>70 µg/24h (193.1 nmol/L), cortisol after 1–mg dexamethasone test>3.0 µg/dL, (>82.8 nmol/L), ACTH<10 pg/mL (<2.2 pmol/L).

Results. BMD was significantly lower in SH+ than SH- patients and controls (LS -0.73±1.43, 0.17±1.33, 0.12±1.21, respectively; FN -0.37±1.06, 0.07±1.09, 0.17±1.02). Patients with SH had higher fractures' prevalence and SDI than those without SH and controls (70.6%, 22.2%, 21.8%, respectively, P<0.0001; 0.31±0.68, 0.39±0.93, 1.35±1.27, respectively, P<0.0001). Fractures and SDI were associated with SH (OR 7.27, 95%CI 3.94–13.41, P=0.0001; =0.352, t=6.241, P=0.0001 respectively) regardless for age, BMD, menopause and gender.

Conclusion. SH is associated with low BMD, high fractures' prevalence and reduced bone quality as measured by SDI.