What is the most common cause of secondary hypertension?

Secondary hypertension is high blood pressure that results from an identifiable and often correctable underlying condition. Renal artery stenosis is the most common cause of secondary hypertension because it involves the narrowing of the arteries that supply blood to the kidneys. This narrowing can lead to reduced blood flow, which consequently triggers the kidneys to release renin, an enzyme that activates the renin-angiotensin-aldosterone system. This system increases blood volume and vascular resistance, resulting in elevated blood pressure.

Obesity, thyroid disease, and Cushing's syndrome are indeed associated with secondary hypertension; however, their occurrence as direct causes is less frequent than that of renal artery stenosis. Obesity can lead to various metabolic changes that contribute to hypertension, while thyroid dysfunction can impact blood pressure through various hormonal pathways. Cushing's syndrome causes hypertension through excess cortisol production, which can lead to water retention and increased blood pressure. Nonetheless, these conditions are less prevalent as causes of secondary hypertension compared to renal artery stenosis in the general population.