High blood pressure can be
divided into two main types based on its cause: primary hypertension and
Causes of Primary Hypertension
Scientists aren’t sure
exactly what causes this common form of high blood pressure, which makes up 90
to 95 percent of cases in adults. Primary hypertension isn’t directly
attributable to any one underlying condition – it is caused by a combination of
factors. However, changes in the arteries over the years are often associated
with higher blood pressure. Such changes include:
- Buildup of fatty deposits inside arteries (atherosclerosis)
- Thickening of artery walls
- Excessive contraction of small arteries (arterioles)
Causes of Secondary Hypertension
This form of high blood
pressure makes up five to 10 percent of cases in adults as well as most cases
in children younger than 10. Secondary hypertension is the direct result of an
underlying health condition that causes blood pressure to shoot up. It can have
a number of causes.
Kidney disease is the most
common cause of secondary hypertension. The kidneys regulate the amount of
fluid in the body. When there is a kidney problem, the volume of blood may
increase. The more blood that must be pumped through the arteries, the higher
the force that is needed.
High blood pressure can be
caused by several forms of kidney disease. Polycystic
kidney disease is an inherited condition characterized by cysts in the
kidneys. Diabetic nephropathy occurs
when diabetes damages the kidneys’ filtering system. Glomerular disease is characterized by swelling of microscopic
kidney filters called glomeruli. High blood pressure can also result from a
blockage inside the kidneys (hydronephrosis)
or narrowing of the arteries leading to them (renovascular hypertension).
The adrenal glands, which sit
atop the kidneys, produce hormones that affect blood pressure. In Cushing’s disease, the adrenal glands
release too much cortisol, which causes blood pressure to rise. In aldosteronism, they release too much
aldosterone, which affects kidney function.
Other glands and their
hormones can play a role, too. In hypothyroidism,
the thyroid gland produces too little thyroid hormone, which can drive up blood
pressure. In hyperthyroidism, the same gland releases too much thyroid hormone.
Ironically, that can also raise blood pressure by increasing the activity of
two other hormones, epinephrine and norepinephrine. In hyperparathyroidism, the parathyroid glands secrete too much
parathyroid hormone, which increases calcium in the blood. That, in turn, can
trigger a blood pressure increase.
Some people are born with a
narrowed aorta, the largest artery in the body. As a result, the heart has to
pump harder to push blood through the aorta. The extra force required raises
blood pressure, particularly in the arms. This condition is called “coarctation
of the aorta.”
Sleep apnea is a disorder
characterized by repeated little pauses in breathing during sleep. This reduces
the amount of oxygen in the body. Insufficient oxygen may damage the lining of
blood vessel walls, making them less effective at regulating blood pressure.
High blood pressure problems
occur in six to eight percent of U.S. pregnancies. Preeclampsia is a potentially serious condition that arises during
the second half of pregnancy and is characterized by high blood pressure and
excess protein in the urine. Gestational
hypertension refers to high blood pressure that starts during pregnancy but
isn’t accompanied by excess urinary protein.
Drugs and supplements
Numerous prescription and
over-the-counter (OTC) medicines can cause or worsen high blood pressure in
certain individuals. These include birth control pills, hormone replacement
therapy, cold-relief medicines, OTC and prescription pain relievers,
antidepressants, asthma medications,
and drugs used for organ transplants. Some herbal supplements, such as ginseng
and Saint John’s Wort, also have this effect. In addition, many illicit drugs,
such as cocaine and methamphetamine, raise blood pressure.
As a general rule of thumb,
the more weight on a person’s body, the higher the amount of blood needed. More
blood pumping through the body leads to additional pressure on the artery
walls, which in turn increases blood pressure. Excess weight can also increase
heart rate, which can also raise blood pressure.