What is the most common cause of secondary hypertension?

The most common cause of secondary hypertension is renal parenchymal disease. This condition encompasses a range of kidney-related issues, including chronic kidney disease, glomerulonephritis, and diabetic nephropathy, among others. These renal disorders can disrupt the body's ability to regulate blood pressure due to changes in fluid balance, renin-angiotensin system activation, and vascular resistance.

When kidney function declines, there is often an increase in sodium retention, leading to increased blood volume, which raises blood pressure. Moreover, kidneys play a crucial role in the regulation of hormonal systems that affect blood pressure, particularly the renin-angiotensin-aldosterone system. Hence, when kidney disease is present, it can significantly influence blood pressure levels.

Other options, while they can cause secondary hypertension, are less prevalent in the general population. Primary aldosteronism, for example, is a specific hormonal disorder that contributes to some cases of secondary hypertension but is not the most common cause. Similarly, oral contraceptive use can lead to hypertension in some women but is less widespread compared to renal parenchymal disease. Cushing's syndrome is another specific endocrine disorder leading to hypertension but is relatively rare compared to the more frequent instances of kidney-related problems.