Hypertension three mainly refers to the hospital under the guidance of a doctor to draw blood tests, including renin, angiotensin and aldosterone three kinds of tests, the purpose of the examination of hypertension three is to exclude the possibility of secondary hypertension. Among all people with hypertension, primary hypertension, called hypertension for which no cause can be found, accounts for 90-95% of the total population. Secondary hypertension accounts for 5%-10% of the population, although it is not a high percentage, the cause of secondary hypertension is clear, and after the cause is identified and effectively removed or controlled, the secondary symptoms can be significantly relieved or even cured. Therefore, if the patient is very young, the possibility of secondary hypertension must be ruled out.