SUN-467 Mild Autonomous Cortisol Secretion With Bilateral Adrenal Disease

Abstract Disclosure: H. Tayyab: None. R. Subramani: None. A. Ullah: None. F. Manas: None. T. Hammad: None. J. Pamula: None. Introduction: Cushing’s syndrome (CS) results from chronic excessive cortisol secretion and is associated with significant morbidity and mortality. Endogenous CS can be ACTH-dependent or ACTH-independent, with the latter comprising 15-20% of cases, commonly due to adrenal adenomas or carcinomas with autonomous cortisol production. Mild autonomous cortisol secretion (MACS), a subset of ACTH-independent CS, has been associated with metabolic and cardiovascular complications. Surgical management, such as adrenalectomy, has shown promise in mitigating these comorbidities, though further research is needed to establish long-term outcomes. Case Presentation: A 59-year-old Caucasian female with a history of hypertension, GERD, coronary artery disease (CAD) and heart failure with reduced ejection fraction (EF 40-45%) presented for evaluation of a right adrenal mass incidentally discovered during a CT chest for pulmonary embolism. Imaging revealed a bilobed right adrenal nodule (3.1 — 1.8 cm superiorly and 1.9 cm inferiorly) with Hounsfield units of 7. She reported a 30-pound weight gain despite a low-carb diet and exercise, as well as elevated home blood pressure readings. Laboratory testing showed an HbA1c of 6%, consistent with prediabetes. On examination, her BMI was 33.6, and physical findings included hyperpigmentation of the anterior and posterior neck and striae. There was no evidence of proximal muscle weakness. Initial labs confirmed hypercortisolism: 24-hour urine-free cortisol: 28 mcg/24h; ACTH: 5 pg/mL, Dexamethasone suppression test: Cortisol failed to suppress (2.4 µg/dL), DHEA-S: 17 mcg/dL; Salivary cortisol and catecholamine levels were within normal limits. MRI revealed bilateral adrenal involvement with mild left adrenal adenomatous hyperplasia. Adrenal vein sampling confirmed cortisol lateralization to the right gland (right adrenal vein cortisol/IVC cortisol = 25.7, left adrenal vein cortisol/IVC cortisol = 6.09), indicating autonomous cortisol secretion from the right adrenal gland. The patient underwent laparoscopic right adrenalectomy. Postoperatively, she was started on glucocorticoid replacement therapy. Follow-up labs showed ACTH recovery (47 pg/mL) and cortisol normalization (16 µg/dL). Discussion: MACS, also known as subclinical Cushing’s syndrome, presents diagnostic challenges due to its overlap with overt CS. It is characterized by low ACTH, failure of cortisol suppression during dexamethasone testing, and low DHEA-S levels, while standard tests such as 24-hour urinary cortisol may remain normal. Evidence suggests surgical management improves metabolic and cardiovascular outcomes in MACS compared to conservative therapy. This case highlights the importance of early diagnosis and the role of adrenalectomy in managing MACS- associated comorbidities. Presentation: Sunday, July 13, 2025