Diabetes Insipidus

Basics

Description

  • Disorder in which large volumes of dilute urine are excreted (polyuria) as an inappropriate response to antidiuretic hormone, arginine vasopressin (AVP)
  • Polyuria defined as >3 L in 24 hr. Often characterized by excessive fluid intake (polydipsia)
  • 2 types:
    • Central diabetes insipidus (DI, CDI; failure or deficiency of AVP release):
      • No AVP to release (loss or malfunction of posterior pituitary neurons)
      • Defective osmoreceptors release AVP only in response to severe dehydration
      • Elevated threshold for AVP release
      • Subnormal amount of AVP released
      • Familial cases have been reported (autosomal dominant)
    • Nephrogenic DI:
      • Lack of renal response to AVP
      • Differentiate from primary polydipsia
      • Some cases are X-linked recessive in males
  • Must be distinguished from primary polydipsia caused by either psychiatric disorder or abnormal thirst

Etiology

  • Central DI:
    • Any condition that disrupts the osmoreceptor–hypothalamus–hypophyseal axis:
    • Highest incident in ages 10–20 yr:
      • Trauma (skull fractures, hemorrhage)
      • Pituitary or hypothalamic surgery
      • CNS neoplasm: DI can be considered a tumor marker:
      • Pituitary adenomas
      • Craniopharyngiomas
      • Germinomas
      • Pinealomas
      • Meningiomas
      • Metastatic tumors
      • Leukemia/lymphoma (Granulomatous)
      • Histiocytosis
      • Sarcoidosis
      • Congenital CNS defects
      • CNS infections (eg, meningitis, encephalitis)
      • Pregnancy (Sheehan syndrome)
      • Idiopathic (autoantibodies, occult tumor)
      • Wolfram syndrome (DI, DM, optic atrophy, deafness)
      • Ethanol
  • Nephrogenic DI:
    • Any condition that impairs the kidney’s response to AVP:
      • Congenital renal disorders
      • Obstructive uropathy
      • Renal dysplasia
      • Polycystic kidney disease
      • Systemic disease with renal involvement
      • Sickle cell disease
      • Sarcoidosis
      • Amyloidosis
      • Drugs:
        • Lithium (most common and persists past drug discontinuation)
        • Amphotericin
        • Phenytoin
        • Aminoglycosides
        • Methoxyflurane
        • Demeclocycline
      • Electrolyte disorders:
        • Hypercalcemia
        • Hypokalcemia

Pregnancy Considerations

  • Typically presents in the 2nd trimester:
    • Unclear etiology, but likely increased production of vasopressinase by the placenta
    • Leads to a decrease in AVP and transient central DI
    • Watch patient closely during anesthesia and periods of water restriction
    • Typically clears after 2–6 wk after delivery
    • Can treat with desmopressin (DDAVP), which resists this additional vasopressinase
  • Sheehan syndrome may cause DI

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