Vasopressin contributes to vasoconstriction by different mechanisms: stimulation of the renin–angiotensin–aldosteron system (RAAS), direct effect on smooth muscle cells, or via secretion of endothelin-1 (ET-1) from endothelial cells, which aggravates endothelial dysfunction [13, 29, 30]. The gene discussed is REN; the disease is endothelial dysfunction.