Pathophysiology

The pathophysiology of hypertension is not fully understood, but it is thought to be caused by several physiological mechanisms, including:

• The balance between cardiac output and peripheral vascular resistance

Maintenance of normal blood pressure is a balance between cardiac output and peripheral vascular resistance. When peripheral vascular resistance increases, blood pressure rises. Blood pressure elevation can also be related to a raised cardiac output

• The renin-angiotensin-aldosterone system

Renin is secreted from the kidneys in response to reduced salt intake or low blood pressure, or via stimulation from the sympathetic nervous system. Renin converts angiotensinogen to angiotensin I, which is converted by angiotensin converting enzyme (ACE) to angiotensin II. Angiotensin II is a vasoconstrictor which causes a rise in blood pressure; it also stimulates the release of aldosterone, causing a rise in blood pressure due to sodium and water retention. Antihypertensive medicines have an effect at different points of the renin-angiotensin system

• High salt intake

Higher than recommended salt intake can produce a higher circulating volume in the blood, leading to increased blood pressure

• Obesity

Obesity can cause hypertension via three main mechanisms: compression of the kidneys by central fat, activation of the renin-angiotensin-aldosterone system, and increased sympathetic nervous system activation.