Diabetes Insipidus

Basics

Basics

Basics

Description

Description

Description

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

Epidemiology

Epidemiology

Epidemiology

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

Risk Factors

Risk Factors

Risk Factors

Genetics

Genetics

Genetics

  • Rare genetic causes of central diabetes insipidus (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

Pathophysiology

Pathophysiology

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

Etiology

Etiology

Etiology

  • Insufficient antidiuretic hormone secretion
    • Traumatic or postsurgical
    • Nonaccidental injury
    • Related to tumor invasion of posterior pituitary
    • Extension from anterior pituitary/suprasellar region: optic glioma, rarely adenomas
    • Hypothalamic: germinoma, craniopharyngioma, meningioma
    • Lymphoma
    • Granulomas: histiocytosis, sarcoidosis
    • Metastatic carcinoma
    • Post–severe ischemic or hypoxic injury to the brain
    • Familial (autosomal dominant)
    • Congenital malformation of CNS
    • Infection: viral encephalitis, meningitis, tuberculosis
    • Increased metabolic clearance of antidiuretic hormone (gestational 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 the medullary concentrating gradient due to excessive free water intake relative to solute intake
ALERT
Pitfalls
  • Management of patients without an intact thirst mechanism and of newborns is difficult.
  • Patients with psychogenic polydipsia may fail a water deprivation test because prolonged excessive water intake can wash out the renal medullary gradient required for concentrating the urine.
  • Surreptitious water intake during water deprivation test
  • Idiopathic, acquired DI can be caused by slowly growing brain tumors not visible on the initial magnetic resonance image.

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