What is the primary cause of secondary hypertension?

Secondary hypertension is characterized by high blood pressure that results from an underlying medical condition. Among the options provided, renal disease is recognized as the primary cause of secondary hypertension. This is primarily due to conditions such as chronic kidney disease or renal artery stenosis, where the kidneys play a pivotal role in regulating blood pressure through the renin-angiotensin-aldosterone system. When kidney function is compromised, this system can become dysregulated, leading to increased blood pressure.

While obesity, smoking, and stress can contribute to primary hypertension, they do not directly cause hypertension through identifiable medical conditions. Obesity often leads to primary hypertension through mechanisms such as increased blood volume and cardiac output. Smoking contributes by damaging blood vessels and promoting atherosclerosis. Stress can temporarily elevate blood pressure, but it is not a definitive cause of long-term hypertension. Therefore, renal disease stands out as the main cause of secondary hypertension due to its direct physiological impact on blood pressure regulation.