Abstract： To the Editor:A 56-year-old Chinese man was referred to Peking Union Medical College Hospital because of polydipsia (9000 ml/24 h) and polyuria (7000 ml/24 h) for over 20 days accompanied with intermittent moderate headache in frontal and temporal areas of both sides for about 2 weeks.The patient underwent a brain magnetic resonance imaging (MRI) with contrast in a local healthy facility,revealing that there was an irregular pituitary lesion measuring 1.1 cm × 1.4 cm × 2.2 cm.Apparently,the diagnosis of central diabetes insipidus (DI) was made,but the pituitary lesion remained to be elucidated.The patient received desmopressin acetate tablets (1.2 mg,q.n.) to ameliorate polydipsia (5000 ml/24 h) and polyuria (4000 ml/24 h).