SIADH (Syndrome of Inappropriate Anti-Diuretic Hormone secretion)

Definition

ADH secretion inappropriate to osmotic and volume state (ADH is usually secreted in hyperatraemia/hypovolaemia)

Diagnostic criteria

• Normovolaemic
• No cardiac, renal, hepatic or endocrine dysfunction
• P_osm
• U_osm > P_osm
• U_Na < 20mmol/L
• Corrected with water restriction

Causes

• CNS disorders
• Pulmonary diseases
• Ectopic ADH production from tumours
• Drugs (opiates, NSAIDS, thiazides, chlorpropramide, MAO-I/TCA, vincristine/vinblastine)