SAT-473 Unilateral Adrenalectomy in a Patient With Overt Cushing Syndrome Caused by Primary Bilateral Macronodular Adrenal Hyperplasia: A Temporizing Measure

Abstract Disclosure: K. Liang: None. J. Kelly: None. F. Khan: None. P.E. Knapp: None. F.T. Drake: Corcept Therapeutics. M.J. Ritter: None. Background: Primary bilateral macronodular adrenal hyperplasia (PBMAH) is a rare cause of Cushing syndrome (less than 2% of cases) often discovered incidentally by imaging tests. Bilateral adrenalectomy is currently the recommended treatment for PBMAH causing overt Cushing syndrome (24-hour urine cortisol > 2-3 times the upper limit of normal [ULN]), but this can be a difficult decision for asymptomatic patients since the resulting adrenal insufficiency requires lifelong steroid replacement and carries long-term risks. Clinical Case: A 36-year-old woman from South America who presented to the ED with abdominal pain and vomiting was diagnosed with diabetic ketoacidosis, with glucose of 431 mg/dL (70-100 mg/dL), hemoglobin A1C of 10.7% (4.0-6.0%), pH of 7.11 (venous, 7.32-7.42), an anion gap of 22 (7-16) and ketonuria. Abdominal CT showed an incidental finding of multiple bilateral adrenal nodules, with the largest in the right adrenal measuring 1.7 cm and the largest in the left measuring 1.8 cm. Despite being generally asymptomatic prior to admission, she was subsequently diagnosed with ACTH-independent Cushing syndrome caused by PBMAH, with a positive overnight 1 mg dexamethasone suppression test (cortisol level of 23.2 µg/dL, n<1.8 µg/dL), 24-hour urine cortisol of 291.4 µg/day (4.0-50.0 µg/day) and ACTH level of 6 pg/mL (6-50 pg/mL). Adrenal vein sampling and aberrant receptor testing were deferred, as neither was likely to affect management. Genetic testing for ARMC5 and KDM1A gene mutations were sent. After discussion with the patient, a decision was made to first proceed with a unilateral adrenalectomy to avoid the immediate need for steroid replacement. She subsequently underwent a left adrenalectomy, and a 1-day post-op morning cortisol level was 13.6 µg/dL (4.0-23.0 µg/dL). Her hyperglycemia was noted to have improved 1 month post-op, on continued treatment with insulin glargine and dulaglutide. Conclusion: Although PBMAH more commonly presents as mild autonomous cortisol secretion, the patient’s 24-hour urine cortisol at the time of diagnosis was nearly 6 times the ULN, consistent with overt Cushing syndrome. Despite bilateral adrenalectomy being the recommended treatment in this case, a unilateral adrenalectomy was performed initially (as part of a staged surgical approach) to avoid the immediate development of adrenal insufficiency. While a future right adrenalectomy will be required, the patient’s clinical stability and improved glycemic control suggest a staged approach to adrenalectomy may reasonably be considered in some cases of overt Cushing syndrome caused by PBMAH. A post-op 24-hour urine cortisol will guide timing of the eventual right adrenalectomy and may inform a possible role for pharmacological bridging strategies. This case underscores the importance of shared decision-making with patients and highlights the management challenges of PBMAH. Presentation: Saturday, July 12, 2025