Blood pressure is a measure of the force the heart uses to pump blood through the body. Blood pressure is measured as two numbers: the systolic over diastolic. Normal blood pressure is under 120/80. Pre-hypertension is defined as being a systolic of 120 to 139 or diastolic of 80 to 89, and hypertension as systolic of 140 or greater or a diastolic of 90 or greater. Diseases causing hypertension come in two categories: essential or unknown causes and those secondary to another process.
Essential
Essential, or primary, hypertension comprises about 90 to 95 percent of the cases of high blood pressure. Essential hypertension has no identifiable cause, is associated with certain risk factors, according to MayoClinic.com. The risk for hypertension increases with age and a family history of hypertension. In addition, people of some races are more prone to hypertension. Risk factors that can be modified include obesity, smoking, exercise, sodium intake, stress and alcohol.
Cardiovascular
According to the American Academy of Family Physicians, some types of cardiovascular diseases lead to high blood pressure. In a condition called aortic regurgitation, the one-way valve separating the left side of the heart from the aorta leaks blood back from the aorta into the heart. The heart may compensate for this by beating more forcefully. In people born with another condition called aortic coarctation, the heart has a narrow aorta, and the blood flowing out to the body is under higher pressure as a result.
Kidney
Various kidney diseases can also cause hypertension. In a condition called renal artery stenosis, one of the arteries leading to the kidneys becomes narrowed. In older people this may be due to the buildup of plaque from fats and cholesterol, but it may also occur in younger people due to the growth of fibrous tissue in the blood vessel wall. Renal stenosis causes the kidney to raise the blood pressure in order to receive more blood.
Hormones
Various hormonal imbalances can induce high blood pressure. Cushing's disease is a disorder of excess cortisol, a stress hormone produced by the adrenal gland. Crohn's disease is similar in that an excessive amount of an adrenal hormone leads to hypertension, but in this case it is caused by the hormone aldosterone, which retains sodium and water while discarding potassium. A tumor called a pheochromocytoma releases epinephrine, commonly known as adrenalin, that raises blood pressure. Imbalances of the thyroid or parathyroid hormones can also cause hypertension.
Drug Induced
Certain drugs can also cause secondary hypertension. Some of these include oral contraceptive pills; glucocorticoids such as prednisone and other agents which suppress the immune system; NSAIDs such as ibuprofen; anabolic steroids; the anti-Parkinson's drug bromocriptine; some weight-loss drugs; and stimulants such as nicotine, amphetamines and cocaine.
