Concurrent onset of type 2 diabetes mellitus and central diabetes insipidus in an adult male

Polyuria is a relatively common symptom which can be caused by a wide range of conditions including uncontrolled diabetes mellitus but also the more rare central diabetes insipidus. The association of the two diagnoses in adult patients is extremely rare. We report the case of a 43-year-old male with significant polyuria and polydipsia (>10 l/24 h) developed progressively over almost a year. Six months before admission in our department, uncontrolled type 2 DM was diagnosed and polyuria was interpreted as a result of his significant glycosuria. However, despite adequate sulfonylurea treatment with normalization of glycemic levels, polyuria persisted and even worsened. Upon admission, polyuria with a very low urine specific gravity and osmolality was noted (suggestive of increased water loss). A water deprivation test was performed and confirmed central diabetes insipidus. Treatment with oral desmopressin was initiated and polyuria disappeared. The concomitant occurrence of DM and DI is extremely rare in adult patients. In such a rare situation, polyuria is usually attributed to uncontrolled DM and concurrent DI can be easily overlooked. Low urine specific gravity and osmolality as well as persistence of polyuria despite adequate control of DM are useful clues to reach the correct diagnosis.