Diabetes insipidus is best described as:

• A. Overproduction of ADH causing water retention
• B. Dehydration
• C. Excessive aldosterone causing hyponatremia
• D. A deficiency of ADH stimulation leading to excessive urination and thirst

Answer: (D)

Diabetes insipidus is about a problem with antidiuretic hormone activity. ADH normally makes the kidneys’ collecting ducts permeable to water, so the body reabsorbs water and urine becomes concentrated. When ADH stimulation is deficient, or the kidneys don’t respond to it, water reabsorption drops dramatically. As a result, legs/urine volume becomes very large and the person feels intense thirst to compensate. This combination of excessive urination and polydipsia is the defining feature, which is why the best description is a deficiency of ADH stimulation leading to excessive urination and thirst.

The other ideas describe different scenarios: too much ADH would cause water retention and hyponatremia, not DI; aldosterone-related effects are not the issue in DI; dehydration can occur with DI but is a consequence, not the mechanism.