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.journal article10.1177/14703203251347397