SUN-409 Postoperative adrenal insufficiency in patients with mild autonomous cortisol secretion

Abstract Disclosure: B. Salama: None. O. Hamidi: None. T.S. Wang: None. A. Sada: None. M.A. Habra: None. P. Dogra: None. A.P. Dackiw: None. S.C. Oltmann: None. S. Mirfakhraee: None. I. Lingvay: None. T. Mckenzie: None. T. Foster: None. M. Lyden: None. B. Dy: None. V. Balderrama Brondani: None. I. Bancos: None. Background: Patients with mild autonomous cortisol secretion (MACS) are at risk for adrenal insufficiency (AI) after unilateral adrenalectomy. Guidelines recommend initiating glucocorticoid replacement post-adrenalectomy. However, identifying patients at risk and accurately diagnosing AI can enable individualized management. Objectives: Determine the prevalence, duration and predictors of postoperative AI after unilateral adrenalectomy for MACS and compare baseline and peak cortisol post cosyntropin stimulation test (CST) In diagnosing AI. Methods: We conducted a multicenter retrospective cohort study of patients with MACS who underwent unilateral adrenalectomy and post-operative CST evaluation between January 1, 2013, and August 31, 2024. MACS was defined as cortisol >1.8 mcg/dL following overnight administration of 1 mg dexamethasone (DST-cortisol). AI was diagnosed when post-operative day 1 early morning baseline cortisol was <10 μg/dL and/or CST peak cortisol was <18 μg/dL. Baseline and peak cortisol levels were considered concordant when both met cut-offs. Biochemical (BSS) and clinical (CSS) severity scores were calculated. Results: Among 281 adults with MACS (80% women, median age 57 years, interquartile range [IQR] (47-64), the median adenoma size was 3.0 cm (IQR, 2.3-3.9), and 62 (22%) had bilateral disease. The median BSS was 4 (IQR, 3-5), and the median CSS was 6 (IQR, 2-11). Postoperative AI was diagnosed in 153 (54.5%) patients. A multivariable analysis showed that a higher BSS (OR = 1.17, 95% CI 1.01-1.36) and younger age at diagnosis (OR = 0.64, 95% CI 0.50-0.81), but not sex, BMI, or laterality, were associated with AI. Diagnosis of AI was concordant based on the baseline and peak CST cortisol cutoffs in 78% of patients. Diagnosis of AI was discordant in 22%: in 35 patients (12%), baseline cortisol was <10 μg/dL, but CST peak cortisol was ≥18 μg/dL, and in 28 cases (10%), baseline cortisol was ≥10 μg/dL, but CST peak cortisol was <18 μg/dL. Patients with bilateral MACS were more likely to have discordant results (32% vs. 19%, P < 0.001). During a median postoperative follow-up period of 15.4 months, 108 patients (70.6%) recovered from AI. The median time to recovery was 3.9 months (IQR, 3-5.9), with 41% recovering by 3 months, 60% by 6 months, and 73% by 12 months. The median time to recovery was associated with baseline BSS: mild: 3 months, moderate: 4.7 months, and severe: 14.5 months. Conclusion: We found that more than half of patients with MACS develop postoperative AI, with 50% recovering by 4 months post-surgery. BSS was associated with both the development and duration of AI. Baseline and CST peak cortisol results were concordant only in 78% of patients, thus performing both should be considered for an accurate diagnosis of AI. Presentation: Sunday, July 13, 2025