[A case of central diabetes insipidus caused by metastatic small cell lung cancer]

A 58-year-old man was admitted to our hospital because of cough, polydipsia and polyuria. Chest CT films showed mediastinal lymphadenopathy, nodules in the lung fields, and pleural effusion. Histopathologic examination of transbronchial biopsy specimens showed oat cell carcinoma. MRI films revealed tumorous swelling of the pituitary stalk. Central diabetes insipidus caused by pituitary metastasis of small cell lung cancer was diagnosed. After treatment with whole-brain irradiation and chemotherapy, the size of the swollen pituitary stalk was reduced and his urine volume decreased. He died of respiratory insufficiency 15 months after the initial diagnosis. No recurrence of pituitary metastasis was apparent. This was a rare case of central diabetes insipidus caused by pituitary metastasis of small cell lung cancer successfully treated with radiotherapy and chemotherapy.