Final answer:
Exogenous ADH would be an effective treatment for the condition known as diabetes insipidus, which is characterized by polyuria and extreme thirst.
Step-by-step explanation:
The patient in this scenario is experiencing polyuria and extreme thirst, which are characteristic symptoms of diabetes insipidus. This condition is caused by chronic underproduction of antidiuretic hormone (ADH) or a mutation in the ADH receptor. ADH helps the kidneys retain water, so administering exogenous ADH would be an effective treatment for diabetes insipidus.