Abstract Introduction Small cell lung carcinoma is one of the most common causes of biochemical hypercortisolism, presenting as a paraneoplastic syndrome. The clinical presentation of severe hypokalemia in the context of metabolic alkalosis, with bicarbonate levels exceeding 50 mEq/L, in a patient denying any toxic ingestion, should raise suspicion for a possible ectopic ACTH-secreting neoplasm. Although cortisol itself does not possess significant mineralocorticoid activity, when levels are excessively elevated, it can exert mineralocorticoid-like effects, mimicking aldosterone and leading to electrolyte disturbances, as observed in this case. In a patient with liver metastases, the most common primary tumor sites include the colorectum, pancreas, breast, lung, and skin (melanoma). Case Presentation An elderly male in his 70s with a history of heavy smoking, hypertension, diabetes, severe peripheral artery disease, and bilateral renal artery stenosis presented with severe fatigue and melena. He reported progressive weakness, multiple episodes of melena, and recent emotional distress following his wife’s death. On admission, labs showed anemia, thrombocytopenia, severe hypokalemia potassium 1.8 mEq/L, CO2 50 mEq/L and elevated liver enzymes. ECG revealed sinus rhythm with a prolonged QTc. Despite aggressive potassium replacement, metabolic abnormalities persisted, prompting nephrology consultation. Cortisol levels were 205. A 24-hour urinary cortisol test showed levels exceeding 4,200 µg. CT scan of the abdomen and pelvis with IV contrast revealed suspected diffuse metastatic involvement of the liver. Endoscopic evaluation revealed gastritis and colonic mucosal abnormalities. A chest CT demonstrated a right perihilar infiltrate and significant mediastinal lymphadenopathy. A bronchoscopy with endobronchial ultrasound (EBUS) was performed for diagnostic evaluation, including lavage, biopsy, dilation, and foreign body removal. Pathology results from station 7 lymph node aspiration via EBUS fine-needle biopsy confirmed malignancy, consistent with small cell carcinoma. Discussion Severe hypokalemia in the setting of metabolic alkalosis in a patient with depression following the loss of a loved one was initially suspected to be secondary to possible toxic ingestion. However, further imaging was ordered due to concerns for malignancy in a patient with risk factors such as chronic alcoholism and heavy smoking. The presence of metastatic liver disease shifted the differential diagnosis toward a suspected ectopic ACTH-secreting tumor and finding the primary tumor site, given the significantly elevated cortisol levels. This case highlights the potential for cortisol, at extremely high levels, to exert mineralocorticoid-like activity, mimicking aldosterone and leading to electrolyte disturbances and in this case severe hypokalemia, ultimately presenting as a paraneoplastic syndrome. This abstract is funded by: None
Martinez et al. (Fri,) studied this question.