Aldosterone helps balance how much sodium and potassium are in the blood. When the body produces too much aldosterone, it can cause the blood to hold more sodium than it should. Because sodium binds to water, extra sodium in the blood means there will be extra water in the blood, too. More fluid inside the veins increases the pressure on the veins. This is known as high blood pressure.
Mayo Clinic: High Blood Pressure (hypertension)
American Heart Association: Health Threats from High Blood Pressure