Diabetes Insipidus (Arginine Vasopressin Disorder)

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DESCRIPTION

Polyuria and polydipsia caused by the inability to produce or respond to antidiuretic hormone; also called arginine vasopressin

EPIDEMIOLOGY

Although most cases are secondary to another disease, the incidence depends on primary cause.

ETIOLOGY

  • Insufficient antidiuretic hormone secretion
    • Traumatic or postsurgical
    • Nonaccidental injury
    • Related to brain cancers/metastases
      • Posterior pituitary tumor invasion
      • Extension from anterior pituitary/suprasellar region: optic glioma, rarely adenomas
      • Hypothalamic: germinoma, craniopharyngioma, meningioma
      • Lymphoma
      • Granulomas: histiocytosis, sarcoidosis
      • Metastatic carcinoma
    • Congenital central nervous system (CNS) malformation
    • Post–severe ischemic or hypoxic brain injury
    • Familial (autosomal dominant)
    • Infection: viral encephalitis, meningitis, tuberculosis
    • Increased metabolic clearance of antidiuretic hormone (gestational diabetes insipidus [DI])
    • Drug- or toxin-related: snake venom, tetrodotoxin
    • Autoimmune disorders: hypophysitis (inflammation of the pituitary gland)
    • Psychogenic: excessive water drinking
    • Idiopathic: must observe for many years to exclude slow-growing tumors
  • Unresponsive to antidiuretic hormone
    • Familial or nephrogenic (X-linked dominant and autosomal recessive forms)
    • Tumor-related
    • Urinary tract obstruction, especially in utero
    • Renal medullary cystic disease
    • Electrolyte disturbances: hypokalemia, hypercalcemia (hypercalciuria)
    • Drugs: usually reversible (diuretics, diphenylhydantoin, reserpine, cisplatin, rifampin, lithium [may become permanent], demeclocycline, ethanol, chlorpromazine, volatile anesthetics, foscarnet, amphotericin B)
    • Loss of medullary concentrating gradient due to excessive free water intake relative to solute intake

RISK FACTORS

Genetics

  • Rare genetic causes of central DI are usually autosomal dominant mutations (neuronal degeneration) and rarely recessive (biologically inactive hormone).
  • Nephrogenic DI is usually familial (autosomal recessive or dominant and X-linked).

PATHOPHYSIOLOGY

  • Antidiuretic hormone stimulates the formation of cyclic adenosine monophosphate (cAMP) in the renal collecting ducts, thereby increasing water permeability and increasing free water reabsorption.
  • Lack of antidiuretic hormone effect results in urinary free water loss.
  • Patients with an intact thirst mechanism drink copiously (polydipsia) to compensate for this free water loss.
  • When the thirst mechanism is not intact or access to free water is limited (e.g., infant, developmentally delayed child, or vomiting), severe dehydration can occur.

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