Endocrine Case Histories - Case 25

A 28-year-old male complained of abrupt polydipsia and polyuria. Blood and urine analyses provided the following results:
Fasting blood glucose 93 mg/dL
Serum sodium 145 mEq/L
Serum potassium 2.8 mEq/L
Urine specific gravity <1.005
Urine osmolality <200 mOsm/L
Urine volume 15 L/day
Urine glucose 0

Water deprivation and hypertonic saline infusion do not cause a significant reduction in the polyuria and concentration of urine. Complete water-deprivation results in the following:
Urine specific gravity 1.009
Urine osmolality 225 mOsm/L

However, there is a significant concentration of the urine and a decrease in urinary output following administration of ADH.

1. Define polydipsia and polyuria.

2. Why did the water deprivation and hypertonic saline infusion not result in a concentrated urine?

3. Describe the location of the disorder in this individual.

4. A nasal spray containing a synthetic substance was self-administered to treat this condition. What type of compound was present in the nasal spray?

5. Discuss the hypothalamic-pituitary-target organ pathway for this individual and indicate the normal and pathophysiological conditions involved.

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