Disorders in which ADH levels are not elevated |
Primary polydipsia due to psychosis |
Low dietary solute intake (beer drinker's potomania, tea and toast diet) |
Disorders with impaired urine dilution but normal suppression of ADH |
Advanced renal impairment |
Diuretic-induced hyponatremia |
Disorders with impaired urine dilution due to unsuppressed ADH secretion |
Reduced effective arterial blood volume |
True volume depletion (hypovolemic hyponatremia) |
Heart failure and cirrhosis (hypervolemic hyponatremia) |
Addison's disease |
SIADH (euvolemic hyponatremia) |
CNS disturbances |
Malignancies |
Drugs |
Surgery |
Pulmonary disease |
Hormonal deficiency (secondary adrenal insufficiency and hypothyroidism)* |
Hormone administration (vasopressin, desmopressin, oxytocin) |
Acquired immunodeficiency syndrome |
Impaired urine dilution due to abnormal V2 receptor (nephrogenic SIADH) |
Abnormally low osmostat |
Acquired reset osmostat of chronic illness |
Genetic reset osmostat |
Reset osmostat of pregnancy |
Exercise-induced hyponatremia |
Cerebral salt wasting |
ADH: antidiuretic hormone; SIADH: syndrome of inappropriate ADH secretion; CNS: central nervous system; V2: vasopressin receptor 2.
* Although sometimes placed in a separate category, we include secondary adrenal insufficiency due to hypopituitarism as a cause of SIADH because it presents with similar clinical manifestations as other causes of the syndrome. Hypothyroidism must be severe to cause clinically important hyponatremia.