Dexamethasone Nonsuppression in Primary Aldosteronism: Associations With Adrenal Imaging Findings

BACKGROUND: The 1-mg dexamethasone suppression test (DST) nonsuppression is increasingly recognized beyond adrenal incidentaloma, but its prevalence and clinical significance in patients evaluated for primary aldosteronism (PA) remain unclear, particularly in those without adrenal nodules. METHODS: In this prospective observational study, consecutive patients with hypertension suspected of PA underwent standardized hormonal evaluation, including the 1-mg DST. DST nonsuppression was defined as post-DST serum cortisol >1.8 μg/dL in the absence of overt Cushing's syndrome. Patients were classified as non-PA or confirmed PA and further stratified by adrenal nodules status on computed tomography. Associations with DST nonsuppression were examined using multivariable logistic regression and propensity score-based analyses, with overlap weighting as the primary approach. RESULTS: Among 883 patients who completed the 1-mg DST, DST nonsuppression was observed in 12.2%. Its prevalence showed an increasing pattern across groups, being lowest in individuals without PA, intermediate in patients with PA without adrenal nodules, and highest in those with adrenal nodules. Adrenal nodules were independently associated with DST nonsuppression (odds ratio, 2.68 [95% CI, 1.01-7.12]), with consistent findings across propensity score-based analyses. Among patients with PA without adrenal nodules, DST nonsuppression was associated with lower estimated glomerular filtration rate and a higher prevalence of chronic kidney disease. CONCLUSIONS: In the high-risk population with PA, DST nonsuppression was not randomly distributed across predefined groups and was independently associated with adrenal nodules. Even in the absence of adrenal nodules, DST nonsuppression was associated by less favorable renal markers, supporting its consistent association with clinical characteristics in patients with PA, rather than implying a distinct biochemical characteristic.