Opportunistic CT Screening for Lumbar Vertebral Trabecular Attenuation in Adrenal Incidentaloma Patients with Mild Autonomous Cortisol Secretion

Abstract

To compare lumbar vertebral trabecular attenuation using CT-based Hounsfield unit (HU) measurements among patients with adrenal incidentalomas (AIs) with mild autonomous cortisol secretion (MACS), non-functioning adrenal incidentalomas (NFAIs), and controls. This retrospective study included 507 patients with AIs who underwent non-contrast abdominal CT. The study sample comprised 121 patients divided into NFAI [cortisol ≤ 1.8 µg/dL following dexamethasone suppression test (DST); n = 76] and MACS (cortisol > 1.8 µg/dL following DST; n = 45) groups. The control group consisted of 48 age- and gender-matched patients. Two radiologists independently measured trabecular HU values in L1–L5 vertebrae. Predictors of low bone mineral density (BMD) (L1 HU < 110) were evaluated using multivariate analyses. A total of 169 patients (mean age, 59 years ± 10 [SD], 50 men) were evaluated. No significant differences existed between groups in age or gender. Mean L1 and L2 HU values were significantly lower in the MACS group (L1: p = 0.027; L2: p = 0.014). Inter-observer reliability was excellent (ICC: 0.932–0.982). A strong correlation was observed between mean L1 HU and lumbar DXA T-score (r = 0.895; p < 0.001). Multivariate analysis identified age, parathyroid hormone level, and patient group as independent predictors of L1 HU < 110. Low BMD risk was significantly lower in the NFAI group (OR = 0.232; p = 0.009). MACS was associated with low trabecular bone attenuation in the upper lumbar vertebrae. Opportunistic CT screening may contribute to bone health risk stratification in AI patients without additional radiation exposure.