Secondary hypertension

DEFINITION

Secondary hypertension (secondary high blood pressure) is high blood pressure that’s caused by another medical condition. Secondary hypertension differs from the usual type of high blood pressure (essential hypertension), which is often referred to simply as high blood pressure. Essential hypertension, also known as primary hypertension, has no clear cause and is thought to be linked to genetics, poor diet, lack of exercise and obesity.

Secondary hypertension can be caused by conditions that affect your kidneys, arteries, heart or endocrine system. Secondary hypertension can also occur during pregnancy.

Proper treatment of secondary hypertension can often control both the underlying condition and the high blood pressure, which reduces the risk of serious complications — including heart disease, kidney failure and stroke.

CAUSES

A number of conditions can cause secondary hypertension. These include:

• Diabetes complications (diabetic nephropathy). Diabetes can damage your kidneys’ filtering system, which can lead to high blood pressure.
• Polycystic kidney disease. In this inherited condition, cysts in your kidneys prevent the kidneys from working normally and can raise blood pressure.
• Glomerular disease. Your kidneys filter waste and sodium using microscopic-sized filters called glomeruli that can sometimes become swollen. If the swollen glomeruli can’t work normally, you may develop high blood pressure.
• Renovascular hypertension. This is a type of secondary hypertension caused by narrowing (stenosis) of one or both arteries leading to your kidneys. Renovascular hypertension can cause severe hypertension and irreversible kidney damage. It’s often caused by the same type of fatty plaques that can damage your coronary arteries (atherosclerosis) or a separate condition in which the muscle and fibrous tissues of the renal artery wall thicken and harden into rings (fibromuscular dysplasia).
• Cushing syndrome. In this condition, corticosteroid medications themselves may cause secondary hypertension, or hypertension may be caused by a pituitary tumor or other factors that cause the adrenal glands to produce too much of the hormone cortisol. This raises blood pressure.
• Aldosteronism. In this condition, a tumor in the adrenal gland, increased growth of normal cells in the adrenal gland or other factors cause the adrenal glands to release an excessive amount of the hormone aldosterone. This makes your kidneys retain salt and water and lose too much potassium, which raises blood pressure.
• Pheochromocytoma. This rare tumor, usually found in an adrenal gland, increases production of the hormones adrenaline and noradrenaline, which can lead to long-term high blood pressure or short-term spikes in blood pressure.
• Thyroid problems. When the thyroid gland doesn’t produce enough thyroid hormone (hypothyroidism) or produces too much thyroid hormone (hyperthyroidism), high blood pressure can result.
• Hyperparathyroidism. The parathyroid glands regulate levels of calcium and phosphorus in your body. If the glands secrete too much parathyroid hormone, the amount of calcium in your blood rises — which triggers a rise in blood pressure.
• Coarctation of the aorta. With this defect you’re born with, the body’s main artery (aorta) is narrowed (coarctation). This forces the heart to pump harder to get blood through the aorta and to the rest of your body. This, in turn, raises blood pressure — particularly in your arms.
• Sleep apnea. In this condition, often marked by severe snoring, breathing repeatedly stops and starts during sleep, causing you to not get enough oxygen. Not getting enough oxygen may damage the lining of the blood vessel walls, which may make your blood vessels less effective in regulating your blood pressure. In addition, sleep apnea causes part of the nervous system to be overactive and release certain chemicals that increase blood pressure.
• Obesity. As you gain weight, the amount of blood circulating through your body increases. This puts added pressure on your artery walls, increasing your blood pressure. Excess weight often is associated with an increase in heart rate and a reduction in the capacity of your blood vessels to transport blood. In addition, fat deposits can release chemicals that raise blood pressure. All of these factors can cause hypertension.
• Pregnancy. Pregnancy can make existing high blood pressure worse, or may cause high blood pressure to develop (pregnancy-induced hypertension or preeclampsia).
• Medications and supplements. Various prescription medications — such as pain relievers, antidepressants and drugs used after organ transplants — can cause or aggravate high blood pressure in some people. Birth control pills, decongestants and certain herbal supplements, including ginseng, licorice and ephedra (ma huang), may have the same effect. Many illegal drugs, such as cocaine and methamphetamine, also increase blood pressure.

SYMPTOMS

Like primary high blood pressure (hypertension), secondary hypertension usually has no specific signs or symptoms, even if your blood pressure has reached dangerously high levels.

Some people may experience headaches from secondary hypertension, but it’s difficult to know if high blood pressure or something else is causing the headaches.

If you’ve been diagnosed with high blood pressure, having any of these signs may mean your condition is secondary hypertension:

• High blood pressure that doesn’t respond to blood pressure medications (resistant hypertension)
• Very high blood pressure — systolic blood pressure over 160 millimeters of mercury (mm Hg) or diastolic blood pressure over 100 mm Hg
• A blood pressure medication or medications that previously controlled your blood pressure no longer work
• Sudden-onset high blood pressure before age 30 or after age 55
• No family history of high blood pressure
• No obesity

When to see a doctor

If you have a condition that can cause secondary hypertension, you may need your blood pressure checked more frequently. Ask your doctor how often to have your blood pressure checked.