Either cerebral salt wasting (CSW), or the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) was regarded as the possible pathogenesis of hyponatraemia (Van Embden et al., 1993; Zhang et al., 1999; Reed et al., 2004; Tsenova et al., 2005; Mihailidou et al., 2012). This evidence concerns the gene AVP and Down syndrome.