B80-5-30 The Tumor Behind the Ketones: Ectopic Acth Secretion From Lung Cancer Presenting as Dka

Abstract We report a case of a 66-old man with a past medical history of type 2 diabetes and heavy tobacco use who presented with progressive generalized weakness and poor oral intake. On admission, physical examination was largely unremarkable except for cachexia and muscle wasting. He was noted to have severely elevated blood pressure that remained difficult to control despite antihypertensive therapy. Laboratory studies revealed marked hyperglycemia, a high anion gap metabolic acidosis, and profound hypokalemia. Urinalysis showed large amounts of glucose and ketones, consistent with diabetic ketoacidosis. His A1c was 11.7%. Paradoxically, the patient remained hypernatremic despite treatment with isotonic fluids and persistently hypokalemic despite aggressive potassium replacement. These findings raised concern for an underlying mineralocorticoid or hypercortisolemic state. Chest X-ray demonstrated a right hilar consolidation concerning for pneumonia or an underlying mass. Endocrine evaluation revealed markedly elevated adrenocorticotropic hormone and cortisol levels, with normal aldosterone levels and an aldosterone-to-renin ratio 20, findings suggestive of ectopic adrenocorticotropic hormone secretion. The patient was started on spironolactone, which resulted in improved blood pressure control and partial correction of hypokalemia. Ketoconazole was initiated for cortisol suppression with close monitoring of liver function. Computed tomography of the chest revealed a right upper-lobe mass causing airway obstruction and extensive mediastinal and hilar lymph node enlargement, along with a lucent lesion at the T12 vertebra concerning for bone involvement. These findings were highly suspicious for malignancy, and small cell lung cancer was considered most likely given the patient’s heavy smoking history. A bronchoscopy with endobronchial ultrasound-guided biopsy was planned for pathologic confirmation; however, the patient declined further diagnostic procedures and left the hospital against medical advice after clinical stabilization. This case emphasizes the importance of maintaining a broad differential diagnosis when evaluating patients with persistent metabolic abnormalities or atypical presentations of diabetic ketoacidosis. The presence of resistant hypertension, refractory hypokalemia, and hypernatremia should prompt evaluation for endocrine or paraneoplastic causes such as ectopic adrenocorticotropic hormone secretion. Early diagnosis relies on biochemical testing of cortisol and adrenocorticotropic hormone levels with failure to suppress with dexamethasone testing, followed by imaging and tissue confirmation. Management includes the use of cortisol synthesis inhibitors such as ketoconazole or metyrapone, mineralocorticoid antagonists such as spironolactone, and definitive treatment of the underlying malignancy through surgery and or chemotherapy. Early recognition and coordinated multidisciplinary management involving pulmonology, endocrinology, critical care, and oncology are essential to improve outcomes and prevent recurrent metabolic crises. This abstract is funded by: None