Secondary hypertension, also known as symptomatic hypertension, is one of the symptoms that arise during the development of certain diseases and can be controlled by correcting its cause. Some patients can be cured surgically, and even if they cannot be cured surgically, they can be treated properly and reasonably for the cause, thus reducing the complications, disability and death rates of secondary hypertension. It is a deep-rooted concept among many physicians that more than 90% to 95% of hypertensive patients have primary hypertension and secondary hypertension accounts for <10% of hypertension. However, with the development of medical diagnostic techniques, the detection rate of secondary hypertension has increased significantly compared to the past. In primary hyperaldosteronism, for example, different studies in recent years have reported detection rates of more than 10%; obstructive sleep apnea syndrome (OSAS) may account for >30% of adult hypertensive patients. The detection of secondary hypertension, however, means that the patient can be cured by receiving etiologic treatment, so the assessment of secondary hypertension should always be considered in the clinical management of hypertension. Screening for secondary hypertension 1.Onset age <30 years old and no family history of hypertension or onset age >50 years old, blood pressure level is moderately or severely elevated; 2.Original blood pressure is normal or the blood pressure is smoothly controlled under regular antihypertensive drugs, but suddenly the blood pressure is suddenly difficult to control or the efficacy of the original antihypertensive drugs has decreased; 3.Refractory hypertension, requiring the use of three or more antihypertensive drugs; 4.Acute 4, acute and malignant hypertension, with rapid development of the disease course and severe target organ damage; 5, unreasonable symptoms: muscle weakness, periodic limb paralysis; obvious fear of heat, excessive sweating, wasting; paroxysmal hypertension with headache, palpitations, repeated apnea or breath-holding phenomenon during sleep; 6, asymmetry of blood pressure in both upper limbs found during physical examination or clinical examination, vascular murmurs detected on physical examination, unexplained abnormal renal function, electrolyte Disorders, double kidney unequal size of hypertensive patients. When a hypertensive patient presents with these symptoms, a strict diagnosis should be made and a high suspicion that the patient may have secondary hypertension. There are many causes of secondary hypertension, mainly the following categories: 1, renal hypertension, including renal hypertension and renal vascular hypertension, accounting for about 5% to 10% of the hypertensive population in China. 2, endocrine hypertension, such as primary aldosteronism, pheochromocytoma, cortisol adenoma and other adrenal diseases; and acromegaly, hyperthyroidism, etc. 3, sleep apnea syndrome Intractable hypertension is more closely related to OSAHS, and the prevalence of intractable hypertension in patients with OSAHS can be as high as 80% or more. OSAHS has become one of the most common causes of secondary hypertension. 4, drug-related hypertension is caused by the pharmacological and/or toxicological effects of the drug itself or the interaction between drugs or improper medication methods, resulting in an increase in blood pressure, is one of the causes of secondary hypertension, but also one of the causes of intractable hypertension. 5, single gene hereditary hypertension is a single gene mutation caused by the disease, in line with Mendel’s law of inheritance, accounting for about 1% of patients with hypertension.