When people talk about hypertension, they mainly refer to primary hypertension, which accounts for about 90-95%, while the rest is secondary hypertension. Here is the difference between the two. Primary hypertension, the pathogenesis of which is still unclear, the current scientific research is mostly believed to be the result of a combination of environmental factors and genetic factors. It is speculated that the following may be involved: 1) elevated sympathetic nerve activity; 2) activation of the renin-angiotensin-aldosterone system (RAAS); 3) genetic polymorphisms; 4) neurotransmitters; 5) insulin resistance; 6) vascular endothelial dysfunction; 7) abnormal cell membrane ion transport; 8) inflammatory response, etc. Secondary hypertension, also known as symptomatic hypertension, in this type of disease, the cause is clear, hypertension is only one of the clinical manifestations of the disease, blood pressure can be temporarily or persistently elevated. Generally, blood pressure can return to normal after the cause is removed, the common ones are: a. Renal vascular hypertension. Second, primary aldosteronism. Third, pheochromocytoma, etc. Therefore, when a patient with hypertension arrives at the hospital, the doctor will take a medical history and combine it with necessary ancillary tests such as ECG, ambulatory blood pressure monitoring, and adrenal CT to make a differential diagnosis and finally determine whether the hypertension is primary or secondary, and take effective treatment to keep the blood pressure within the appropriate range.