Hyponatremia, with an incidence of 15 – 22%, is considered when serum sodium levels are < 135 mEq/L (in institutionalized geriatric patients, in 1 – 4% to 7 – 53% cases there have been reported values below 130 mEq/L) [1-3]. Additionally, according to expert panel recommendations the frequency of hyponatremia in hospitalized patients depends on the detected level of hyponatremia . This special condition is highly important to be detected on time because it represents a recognized risk factor of morbidity and mortality, even in asymptomatic patients . Furthermore, it was noticed that a swift correction can induce severe neurological disorders and even death . Therefore, for an adequate treatment management (prophylaxis and therapy) is vital for understanding hyponatremia main causes and the incriminated pathophysiological mechanisms .