Diabetes insipidus is caused by damage to which brain structures?

• A. Renal failure
• B. Pulmonary infection
• C. Cranial surgery, infection, or tumor
• D. Liver disease

Answer: (C)

Central diabetes insipidus occurs when the brain's antidiuretic hormone pathway is damaged, specifically the hypothalamus and/or the posterior pituitary. The hypothalamus makes ADH and sends it to the posterior pituitary, which stores and releases it. If this communication or these structures are injured—such as after cranial surgery, infection, or tumor—the release of ADH drops or stops. Without ADH, the kidneys don’t reabsorb water effectively, so large volumes of dilute urine are produced and thirst increases. The other problems listed involve organ systems outside the brain and don’t disrupt the brain’s ADH pathway in the same way.