A Diagnostic Enigma of Central Versus Nephrogenic Diabetes Insipidus: What Does the Value of Copeptin Signify?

Diabetes insipidus (DI) is a rare disease characterized by hypotonic urine output and polydipsia. We report the case of a 50-year-old male admitted for diabetic ketoacidosis (DKA) in an intensive care unit with sepsis and alcoholic pancreatitis who later developed DI. He had a high copeptin level of >21.4 pmol/L, suggesting DI of nephrogenic origin. At presentation, he had DKA-associated osmotic diuresis. His later finding of elevated copeptin suggesting partial nephrogenic DI created a diagnostic enigma.