Saturday, January 31, 2009

Diabetes insipidus

Clinical Characteristics

Decreased secretion or action of AVP usually manifests as DI, a syndrome characterized by the production of abnormally large volumes of dilute urine. The 24-h urine volume is >50 mL/kg body weight and the osmolarity is <300 mosmol/L. The polyuria produces symptoms of urinary frequency, enuresis, and/or nocturia, which may disturb sleep and cause mild daytime fatigue or somnolence. It is also associated with thirst and a commensurate increase in fluid intake (polydipsia). Clinical signs of dehydration are uncommon unless fluid intake is impaired.

Etiology

Deficient secretion of AVP can be primary or secondary. The primary form usually results from agenesis or irreversible destruction of the neurohypophysis and is variously referred to as neurohypophyseal DI, pituitary DI, or central DI.

Pathophysiology

When the secretion or action of AVP is reduced to <80>

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