Hypertension is divided into two categories: primary hypertension and secondary hypertension. The details are as follows: 1. Primary hypertension: accounts for more than 90% of all hypertension, no clear cause, with elevated blood pressure as the main feature; 2. Secondary hypertension: can be clear cause, also known as symptomatic hypertension, blood pressure is paroxysmal or persistent elevation. Common causes are renal artery stenosis, adrenal adenoma, pheochromocytoma, Cushing’s syndrome, and long-term use of contraceptives, painkillers, hormones, and other drugs that cause elevated blood pressure.