Diabetes Insipidus - Endocrine

Snapshot
- A 30-year-old woman presents to her primary care physician for increased frequency of urinating, thirst, and urinating at night. She was in a car accident about a month ago, where she had head trauma. Since then, she reports that she has noticed this increased frequency of urination. At that time, head imaging had been normal. Her physician decides to conduct a vasopressin challenge. The results show decreased urine volume and increased urine osmolality. Based on these results, she decides to start the patient on desmopressin. (Central diabetes insipidis)

Introduction

Clinical definition
- diabetes insipidus (DI)
  - characterized by excess free water loss and dilute urine

Central vs Nephrogenic Diabetes Inspidus (DI)
	Central DI
Definition	Failure to produce antidiuretic hormone (ADH)	Insensitivity or resistance of the kidneys to ADH in the collecting duct
Etiology	Pituitary tumor, where vasopressin is released Other pituitary injuries autoimmune disease trauma surgery ischemia	Drugs lithium demeclocycline amphotericin B Congenital (rare) Electrolyte abnormalities hypercalcemia hypokalemia
Pathogenesis	↓ ADH, resulting in increased extracellular fluid osmolarity	↑ADH
Vasopressin (DDAVP) challenge	↓ Urine volume and ↑ urine osmolality	No change in urine volume or osmolality

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