Chu, Wen-KaiWen-KaiChuHe, JieJieHePeng, You-BoYou-BoPengFu, Hong-WeiHong-WeiFuVIN-CENT WUYuan, Hong-LingHong-LingYuan2025-07-092025-07-092025-06https://scholars.lib.ntu.edu.tw/handle/123456789/730638Background: While the 1 mg dexamethasone suppression test (DST) is commonly used to diagnose mild autonomous cortisol secretion (MACS), the diagnostic utility of 24-h urinary free cortisol (24-h UFC) in patients with primary aldosteronism (PA) remains unclear. Methods: We prospectively enrolled 274 patients with confirmed PA between January 2017 and January 2020. MACS was defined by a post-DST serum cortisol level >1.8 μg/dL. Results: Among 274 PA patients (42.3% male; mean age, 55.9 ± 11.7 years)), 74 patients (27%) with PA had concomitant MACS while the other 200 patients were not. PA patients concomitant MACS were associated with higher 24-h UFC (OR, 1.91 [95% CI, 1.06–3.41], P = 0.03), older age (OR, 1.04 [95% CI, 1.01–1.07], P = 0.008), and diabetes mellitus (OR, 2.4 [95% CI, 1.12–5.12], P = 0.025). The 24-h UFC above 36 μg was associated with a positive predictive value of 32.6% and a negative predictive value of 77.9% for identifying concomitant MACS. Conclusions: Our study suggested the 24-h UFC less than 36 μg could help exclude MACS in PA cases. Combining this with 1 mg DST enhances accuracy. Additionally, older age and diabetes mellitus were also risk factors for predicting patients with PA concomitant MACS.Urinary cortisol level in exclusion mild autonomous cortisol secretion in the patient of primary aldosteronismjournal article10.1177/14703203251347397