In diabetes insipidus, what is the expected serum sodium status?

• A. Hypokalemia due to excess water retention
• B. Hypernatremia due to decreased water intake
• C. Hyponatremia due to increased sodium loss
• D. Hyponatremia due to increased water retention

Answer: (B)

In diabetes insipidus, the primary issue is the inadequate production or action of antidiuretic hormone (ADH), which leads to an inability to concentrate urine. Consequently, the kidneys excrete a large volume of dilute urine, resulting in increased fluid loss from the body. As fluids are lost, the serum sodium concentration can become elevated due to insufficient water intake or excessive loss of water relative to sodium. This condition is termed hypernatremia, which reflects a higher-than-normal sodium level in the serum.

Patients with diabetes insipidus often experience increased thirst as a compensatory mechanism, urging them to drink more fluids to counterbalance the loss. However, if fluid intake does not meet the losses, the serum sodium levels rise. Thus, the expected serum sodium status in diabetes insipidus is hypernatremia, confirming the correct choice.

The other options do not accurately describe the serum sodium status in diabetes insipidus, as the condition does not typically lead to situations of sodium loss or increased water retention in a way that would cause hyponatremia.