Abnormally low levels of or mutations in AQP2 or V2 receptors can cause polydipsia, polyuria, and associated electrolyte imbalance, resulting in severe dehydration in conditions such as nephrogenic diabetes insipidus (NDI); conversely, excessive AQP2 levels can induce hyponatremia, leading to heart and liver failure [92]. The gene discussed is AQP2; the disease is liver failure.