During hemorrhagic shock, the loss of circulating blood volume reduces oxygen supply to tissues, triggering compensatory mechanisms such as vasoconstriction, increased heart rate, and activation of the renin-angiotensin-aldosterone system.51 While these responses help maintain perfusion to vital organs, tissue hypoxia eventually leads to anaerobic metabolism, lactic acidosis, and organ failure. The gene discussed is REN; the disease is lactic acidosis.