The reliability of these studies is diminished because of three factors: first, the target groups were relatively small; second, most studies were performed in Eastern populations and rural areas; third, copeptin is a marker that can also rise in several other conditions, such as myocardial infarction, polyuria–polydipsia syndrome, hyponatremia, polycystic kidney disease, and metabolic disorders (diabetes mellitus, metabolic syndrome, insulin resistance, infections) [10,12]. This evidence concerns the gene AVP and metabolic syndrome.