Disorders of serum sodium are both the most common and probably most the poorly
understood electrolyte disorders in clinical medicine. In the past few years increased
knowledge about the non-osmotic release of vasopressin and the cloning of vasopressin
receptors and of vasopressin-regulated water channels (AQP2) has enhanced our
understanding of these disorders. Also controversies surrounding the treatment of
hyponatraemic patients have led to well-accepted therapeutic guidelines.