A 34-year-old male presents with a 2-week history of excessive thirst (polydipsia) and urination (polyuria). He reports drinking large amounts of water throughout the day, approximately 6-8 liters, and frequently waking up at night to urinate. Despite drinking large quantities of fluids, he continues to feel parched and has lost about 2 kg of weight in the past week. He denies fever, nausea, vomiting, or any changes in appetite.

His medical history is notable for a previous head injury 4 years ago, which required a brief hospital stay, but he did not experience any symptoms until now. He is otherwise healthy, does not take any medications, and has no significant family history of diabetes or renal disease.

Upon examination, his vital signs are normal, and he is afebrile. He appears well-hydrated but is slightly underweight for his height. No significant findings are noted on the rest of his physical examination. Urinalysis reveals a very low specific gravity, and a serum electrolyte test shows normal sodium and potassium levels, with normal renal function. A water deprivation test is performed, showing continued high urine output despite dehydration, indicating an inability to concentrate urine.

Further testing reveals a low level of antidiuretic hormone (ADH), supporting a diagnosis of central diabetes insipidus. The patient is advised to undergo MRI imaging of the pituitary gland to rule out any structural abnormalities, such as a pituitary tumor.

Management Plan:

The patient is started on desmopressin (DDAVP), a synthetic analog of ADH, to help manage his symptoms. He is educated on the importance of fluid intake and monitoring urine output. Follow-up is scheduled in 2 weeks to assess his response to treatment and monitor for any potential side effects.