Secondary hypertension is mostly considered to be caused by renal diseases, vascular lesions, endocrine system diseases, hypertensive syndrome of pregnancy, etc. There is no saying which type is the most serious. 1. Renal disease: chronic renal disease caused by inflammation or damage to glomeruli and tubules can cause secondary hypertension. 2. Vascular disease: Multiple aortitis or congenital stenosis of blood vessels can lead to decreased blood circulation and metabolism, thus triggering the emergence of secondary hypertension. 3. Endocrine system diseases: primary aldosteronism, cortisolism and long-term use of contraceptives can cause endocrine disorders and secondary hypertension. 4. Gestational hypertension syndrome: women’s heart is compressed with the increase of pregnancy cycle, which induces the appearance of secondary hypertension. There is no such thing as which type of secondary hypertension is the most serious, and it is only according to the actual situation and the degree of disease development that one can judge whether it is serious or not. When secondary hypertension occurs, you can go to the hospital in time to check the cause of the disease and treat it according to your own situation.