AbstractObjectiveTo investigate the effects of simultaneous cortisol cosecretion (CCS) on body composition in computed tomography (CT)‐imaging and metabolic parameters in patients with primary aldosteronism (PA) with the objective of facilitating early detection.DesignRetrospective cohort study.PatientsForty‐seven patients with PA and CCS confirmed by 1‐mg dexamethasone suppression test (DST) with a cutoff of ≥1.8 µg/dL were compared with PA patients with excluded CCS (non‐CCS, n = 47) matched by age and sex.MethodsSegmentation of the fat compartments and muscle area at the third lumbar region was performed on non‐contrast‐enhanced CT images with dedicated segmentation software. Additionally, liver, spleen, pancreas and muscle attenuation were compared between the two groups.ResultsMean cortisol after DST was 1.2 µg/dL (33.1 nmol/L) in the non‐CCS group and 3.2 µg/dL (88.3 nmol/L) in the CCS group with mild autonomous cortisol excess (MACE). No difference in total, visceral and subcutaneous fat volumes was observed between the CCS and non‐CCS group (p = .7, .6 and .8, respectively). However, a multivariable regression analysis revealed a significant correlation between total serum cholesterol and results of serum cortisol after 1‐mg DST (p = .026). Classification of the patients based on visible lesion on CT and PA‐lateralization via adrenal venous sampling also did not show any significant differences in body composition.ConclusionMACE in PA patients does not translate into body composition changes on CT‐imaging. Therefore, early detection of concurrent CCS in PA is currently only attainable through biochemical tests. Further investigation of the long‐term clinical adverse effects of MACE in PA is necessary.