In most cases of high blood pressure (hypertension), there is no known cause. About 6% of the time, however, high blood pressure is caused by another condition or disease. When this happens, it is called secondary hypertension.
Most of the conditions that cause secondary hypertension involve the overproduction of one of the body's hormones. Some of the medical problems that can cause secondary hypertension include:
- Kidney disease. Secondary hypertension can be related to damaged kidneys or to an abnormal narrowing of one or both renal arteries. The renal arteries are the major blood vessels that bring blood to each kidney. When the kidney's blood supply is reduced by a narrowing (called renal artery stenosis), the kidney produces high levels of a hormone called renin. High levels of renin trigger the production of other substances in the body that raise blood pressure, particularly a molecule called angiotensin II.
- Adrenal disease. The adrenal glands sit on top of the kidneys and produce several hormones that help regulate blood pressure. Sometimes, one or both adrenal glands make and secrete an excess of one of these hormones.
Three different types of adrenal gland conditions cause high blood pressure:
- Pheochromocytoma. A tumor of the adrenal gland that overproduces the hormones epinephrine (adrenalin) and norepinephrine (noradrenalin).
- Hyperaldosteronism (also called Conn's syndrome). Both adrenal glands can overproduce the salt-retaining hormone aldosterone or it can arise in a benign adrenal tumor.
- Hypercortisolism (also called Cushing's syndrome). Both adrenal glands can overproduce the hormone cortisol or it can arise in a benign or malignant tumor.
- Hyperparathyroidism. A hormone called parathormone is made by four tiny glands in the neck called parathyroid glands. If the glands produce too much hormone, calcium levels in the blood increase. People with hyperparathyroidism are more likely to have high blood pressure. The exact reason for this association is not known.
Other rare causes of secondary hypertension include:
- Acromegaly. A pituitary tumor that produces too much growth hormone.
- An adrenocorticotrophic hormone (ACTH) producing tumor of the pituitary gland. The pituitary normally makes a small amount of ACTH daily. Excess ACTH production and secretion causes the adrenal glands to overproduce cortisol, raising blood pressure.
- An ACTH producing cancer of the lung.
- Coarctation of the aorta, a malformation of the major blood vessel that carries blood from the heart to the rest of the body.
High blood pressure may be a side effect of medication, such as hormonal contraceptives and non-steroidal anti-inflammatory agents (NSAIDs).
The traditional definition of high blood pressure is a systolic blood pressure (the higher of the two blood pressure numbers) is 140 millimeters of mercury (mm Hg) or above, and the diastolic blood pressure (the lower blood pressure number) is 90 mm Hg or above. People with secondary hypertension often have blood pressure that is more difficult to control with one or two medications. Also, there can be other symptoms related to the medical illness that is causing the hypertension.
For example, a tumor of the adrenal gland called a pheochromocytoma can cause sweating, palpitations, severe anxiety and weight loss. In Cushing's syndrome, there may be weight gain, weakness, abnormal growth of body hair and loss of menstrual periods in women, and the appearance of purple "stretch marks" on the abdomen (abdominal striae). Hyperparathyroidism with elevated calcium levels can cause extreme tiredness, increased urination, constipation and kidney stones. Hyperaldosteronism often causes weakness related to low blood potassium levels.
You doctor will ask you if you have any symptoms related to the medical illnesses that cause secondary hypertension. During a physical examination, your doctor will pay special attention to any sudden weight gain or weight loss, signs of extra fluid in your tissues, abnormal hair growth, and purple marks on your abdomen. You doctor also will check your abdomen for any abnormal masses, and he or she will use a stethoscope to listen for sounds of abnormal blood flow in your kidneys.
Depending on the results of your physical examination, your doctor will order additional tests to pinpoint the cause of your secondary hypertension. For suspected kidney disease, these tests may include blood tests for creatinine and blood urea nitrogen (BUN), urinalysis, and an ultrasound examination of your abdomen to evaluate the size of your kidneys. If there is concern that you may have renal artery stenosis, your doctor may order magnetic resonance imaging (MRI) with magnetic resonance angiography (MRA). Occasionally, a test called a renal arteriogram is ordered.
For pheochromocytoma, your urine or blood may be analyzed for levels of catecholamines (the hormones epinephrine and norepinephrine). For Cushing's syndrome, urine or blood levels of cortisol are measured. For hyperparathyroidism, blood levels of parathormone, calcium and phosphate are measured. For hyperaldosteronism, a blood test for potassium and aldosterone levels are measured.
Coarctation of the aorta usually is suspected based on the younger age of the person, physical exam findings (blood pressure in the arms much higher than blood pressure in the legs) and specific changes seen on chest X-ray.
Secondary hypertension will last as long as the medical problem that is causing it remains untreated.
Most of the medical problems that cause secondary hypertension can't be prevented. This makes secondary hypertension different from essential hypertension, which can be prevented by exercising regularly, restricting salt, following a healthy diet, watching your weight and avoiding smoking.
The treatment of secondary hypertension depends on its cause. When secondary hypertension results from a tumor or a blood vessel abnormality, surgery may be recommended. However, the decision to do surgery is often guided by the age and general health of the patient. For some patients, anti-hypertensive medications may be a safer option than surgery.
Inform you doctor if you have any of the symptoms associated with medical illnesses that cause secondary hypertension, such as unexplained weight change, palpitations, leg swelling (edema), marked fatigue, abnormal hair growth or new purplish stretch marks on your skin.
In many patients with secondary hypertension, high blood pressure can be cured when their underlying medical illness is treated successfully.
National Heart, Lung, and Blood Institute (NHLBI)
P.O. Box 30105
Bethesda, MD 20824-0105
American Heart Association (AHA)
7272 Greenville Ave.
Dallas, TX 75231