Introduction:
Blood pressure is measured in millimeters of mercury (mm Hg) and it has two components: systolic pressure (SBP), the higher number; and diastolic pressure (DBP), the lower number.

SBP represents the pressure that the heart must generate to pump blood to the rest of the body, while DBP refers to the pressure needed to pump blood to the arteries of the heart (coronary arteries). DBP also represents the pressure exerted by the blood between heartbeats. Usually SBP increases as we age. However, after age 60, DBP usually begins to decline because of stiffening of the body’s blood vessels.

Hypertension is defined as: systolic blood pressure (SBP) of 140 mm Hg or greater; or diastolic blood pressure (DBP) of 90 mm Hg or greater.

Symptoms:
Usually hypertension causes no symptoms. However, if blood pressure readings are very high, there may be headaches and fatigue (a tired feeling). Hypertension damages the brain, heart, and kidneys, as well as arteries throughout the body. Because of this, hypertension is a very important risk factor for heart attacks, strokes, and kidney failure.

Diagnosis:
Blood pressure readings of more than 140/90 mm Hg on three consecutive visits over a several month period lead to a diagnosis of hypertension.

Prevention:
Prevention of hypertension involves regular aerobic exercise, salt restriction, adequate intake of fruits and vegetables, avoidance of smoking, a low fat diet, and maintenance of a desirable body weight.

Secondary Hypertension
Introduction:
Secondary hypertension is high blood pressure which is caused by a specific medical illness, often related to a change in hormone secretion or kidney function. In secondary hypertension, a specific medical reason for the increased blood pressure can be identified and possibly corrected. This distinguishes secondary hypertension from essential hypertension (the most common type of hypertension), where high blood pressure may be the only symptom and the underlying medical cause remains unknown.

Cause:

Kidney disease – Secondary hypertension related to kidney (renal) disease is called renal hypertension. It may be due to abnormalities in the way that the kidneys handle sodium and fluids, or it may be triggered by kidney chemicals which make the arteries constrict. Often it is associated with abnormal narrowing of a renal artery, one of the major blood vessels which bring blood to each kidney.

Adrenal disease – Secondary hypertension can be caused due to increased adrenal production of the hormone aldosterone (which makes the body retain sodium) caused by an adrenal tumor or adrenal hyperplasia (abnormal growth of adrenal cells). It may also be due to Cushing’s Syndrome, where the adrenals produce abnormally high amounts of corticosteroid hormones. A pheochromocytoma is a tumor that produces epinephrine and norepinephrine, two catecholamine hormones that stimulate the heart and constrict the arteries.

Hyperparathyroidism – In about one third of patients with hyperparathyroidism (abnormally high levels of hormones produced by the parathyroid gland) increased levels of calcium in the blood may raise blood pressure by damaging the kidneys and/or directly constricting arteries.

Other causes – Other causes of secondary hypertension include: acromegaly (excess production of growth hormone by a tumor of the pituitary gland); coarctation of the aorta (a malformation of the major blood vessel which carries blood from the heart to the rest of the body); and (rarely) use of oral contraceptives.