Renin is a protease secreted by the granule cells of the glomerular parietal apparatus. When renin secretion is increased, it activates the renin-angiotensin-aldosterone system, thereby raising blood pressure and increasing the effective perfusion of the kidney. The factors that can increase renin secretion are often due to a decrease in blood pressure and a decrease in blood flow through the glomerulus, which is then sensed by the glomerular paracellular apparatus and then increases renin secretion, which is also a process of self-regulation in the body. If the effective perfusion of the kidney is insufficient after the decrease of blood flow, the kidney will experience ischemic necrosis. Therefore, after the secreted renin activates the renin-angiotensin-aldosterone system, it will increase the effective perfusion of the kidney, blood pressure, and also the water and sodium can be retained later through the secretion of aldosterone. Therefore, the factor that causes increased renin secretion is actually when there is a situation in the human body, such as a burn or severe diarrhea, hemorrhage, etc., which leads to a drop in blood pressure, which leads to increased renin secretion.