When we talk about hypertension, we are referring to primary hypertension, which accounts for 90% of all cases of hypertension. What causes primary hypertension? This is still not completely understood. It is generally believed that this kind of hypertension is caused by the combination of genetic and environmental factors, the exact cause of primary hypertension cannot be determined, but after the onset of primary hypertension, it can cause different degrees of pathologic damage to the brain, heart, kidneys and other organs, and the hazards of primary hypertension are also mainly in this. About 10% of the hypertension is secondary hypertension. The so-called secondary hypertension, that is to say, there is a reason for the occurrence of hypertension, blood pressure increase is only one of its more prominent symptoms. Common causes of secondary hypertension are: 1, endocrine diseases, such as pheochromocytoma, primary aldosteronism, etc.; 2, renal lesions, such as acute and chronic glomerulonephritis, pyelonephritis, renal artery stenosis, etc.; 3, large-vessel lesions, such as large-vessel sarcoidosis (congenital narrowing of the aorta), multiple large arteries, etc.; 4, gestational hypertension syndrome; 5, cerebral disorders; 6, pharmacogenic factors etc. Therefore, younger patients with hypertension should be examined accordingly to avoid missing the diagnosis of secondary hypertension and losing the chance of curing hypertension.