Brain injury can cause alterations in Na+, K+, Ca2+, and other electrolyte levels, which can be used as a prognostic factor for mortality and morbidity following TBI [158,159,160]; for instance, an excessive release of antidiuretic hormone (ADH) may cause the syndrome of inappropriate antidiuretic hormone secretion (SIADH), leading to water retention and dilutional hyponatremia. This evidence concerns the gene AVP and inappropriate ADH syndrome.