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During the congress, E-Posters will be accessible to all participants on the congress website 24/7, as well as in the E-poster stations in the congress center.
Preparing your E-Poster
Please review the E-Poster format requirements carefully when preparing your E-Poster. Should your E-Poster not meet the mentioned requirements, it may not be displayed as described above.
E-Poster Submission Deadline
Please prepare and upload your E-Poster no later than March 14, 2026 11.59PM CET. After this date, you will no longer be able to prepare and upload your E-poster and it will not be displayed and accessible on the congress website.
Please follow the instructions below to input your abstract title.
Abstract titles should be brief and reflect the content of the abstract.
Paraneoplastic endocrinopathies are well-recognized complications frequently observed in patients with neuroendocrine malignancies such as small cell lung cancer (SCLC). However, the concurrence of both syndrome of inappropriate antidiuretic hormone (SIADH) and Cushing syndrome is rare, with <10 reported cases. This case is unique for its extreme hormonal imbalance and a triphasic pattern of electrolyte disturbances, highlighting diagnostic and management challenges.
An 81-year-old female, with history of localized squamous cell carcinoma of the right lower lung lobe, presented with confusion. Laboratory tests showed severe hyponatremia (110 mmol/L), suggestive of SIADH. Salt tablets were initiated with improvement in her [sodium] levels. CT scan revealed multiple lung and liver nodules, suggestive of disease recurrence. Instead, liver biopsy confirmed small cell lung cancer, for which chemotherapy/immunotherapy was initiated.
Nine months later, she presented with severe hypokalemia (2.3 mmol/L) and alkalosis (CO2 38 mmol/L) but was normonatremic (141) despite not taking her salt tablets. Urine studies revealed renal potassium wasting, and serum studies showed elevated AM cortisol (49.1 mcg/dL) and high ACTH (181 pg/mL). CT scan showed bilateral adrenal thickening. A high-dose dexamethasone suppression test confirmed ectopic Cushing syndrome, so she was started on metyrapone.
Within 48 hours, her [sodium] declined from 138 to 130 mmol/L. Copeptin later came back at >5,000 pmol/L. Tolvaptan was considered, but fluid restriction, salt tablets, and urea normalized her [sodium].
Hyponatremia resolving to hypokalemia/alkalosis and recurring to hyponatremia again should raise the suspicion for dual paraneoplastic syndrome in SCLC. Our patient exhibited a triphasic electrolyte evolution, highlighting an intricate hormonal interplay: hyponatremia due to SIADH, normalization during hypercortisolism, and recurrent hyponatremia after cortisol reduction. The high cortisol's mineralocorticoid activity, overwhelming 11beta-hydroxysteroid dehydrogenase, likely masked hyponatremia, and then metyrapone-induced cortisol suppression may have unmasked a persistent ADH-driven water retention. Anticipating this triphasic course is key to the diagnosis and treatment of a rare dual paraneoplastic syndrome in SCLC.
