Secondary high blood pressure (secondary hypertension) is high blood pressure that's caused by another medical condition. Secondary hypertension can be caused by conditions that affect your kidneys, arteries, heart or endocrine system. Secondary hypertension can also occur during pregnancy.
Secondary hypertension differs from the usual type of high blood pressure (primary hypertension or essential hypertension), which is often referred to simply as high blood pressure.
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.
Like primary hypertension, secondary hypertension usually has no specific signs or symptoms, even if your blood pressure has reached dangerously high levels.
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 180 millimeters of mercury (mm Hg) or diastolic blood pressure over 120 mm Hg
- High blood pressure that no longer responds to medication that previously controlled your blood pressure
- 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.
Many different diseases and health conditions can cause secondary hypertension. Several kidney diseases may cause secondary hypertension, including:
- 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 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 type of high blood pressure is caused by narrowing (stenosis) of one or both arteries leading to your kidneys.
Renovascular hypertension is 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).
Medical conditions affecting hormone levels also may cause secondary hypertension. These conditions may include:
- Cushing syndrome. In this condition, corticosteroid medications 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.
- Aldosteronism. The adrenal glands produce too much 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, produces too much 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 control levels of calcium and phosphorus in your body. If the glands release too much parathyroid hormone, the amount of calcium in your blood rises — which triggers a rise in blood pressure.
Other possible causes of secondary hypertension include:
- Coarctation of the aorta. In this condition, present at birth, 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. As a result, blood pressure increases — 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 it harder for your blood vessels to control 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 flowing through your body increases. This puts added pressure on your artery walls, increasing your blood pressure.
Being overweight also increases the heart rate and makes it harder for your blood vessels to move blood. In addition, fat deposits can release chemicals that raise blood pressure.
- Pregnancy. Pregnancy can make existing high blood pressure worse or cause high blood pressure to develop (pregnancy-induced hypertension or preeclampsia).
Medications and supplements. Various prescription medications — such as pain relievers, birth control pills, antidepressants and drugs used after organ transplants — can cause or worsen high blood pressure in some people.
Over-the-counter 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.
The greatest risk factor for developing secondary hypertension is having a medical condition that can cause high blood pressure, such as kidney, artery, heart or endocrine system problems.
Secondary hypertension can worsen the underlying medical condition you have that's causing your high blood pressure. If you don't receive treatment, secondary hypertension can lead to other health problems, such as:
- Damage to your arteries. This can result in hardening and thickening of the arteries (atherosclerosis), which can lead to a heart attack, stroke or other complications.
- Aneurysm. Increased blood pressure can cause your blood vessels to weaken and bulge, forming an aneurysm. If an aneurysm ruptures, it can be life-threatening.
- Heart failure. To pump blood against the higher pressure in your vessels, your heart muscle thickens. Eventually, the thickened muscle may have a harder time pumping enough blood to meet your body's needs, which can lead to heart failure.
- Weakened and narrowed blood vessels in your kidneys. This can prevent these organs from working properly.
- Thickened, narrowed or torn blood vessels in the eyes. This can result in vision loss.
Metabolic syndrome. This syndrome is a cluster of disorders of your body's metabolism — including increased waist circumference, high triglycerides, low high-density lipoprotein (HDL) cholesterol (the "good" cholesterol), high blood pressure and high insulin levels.
If you have high blood pressure, you're more likely to have other components of metabolic syndrome. The more components you have, the greater your risk of developing diabetes, heart disease or stroke.
- Trouble with memory or understanding. Uncontrolled high blood pressure also may affect your ability to think, remember and learn. Trouble with memory or understanding concepts is more common in people who have high blood pressure.
To diagnose secondary hypertension, your doctor will first take a blood pressure reading using an inflatable cuff, just as your blood pressure is measured during a typical doctor's appointment.
Your doctor may not diagnose secondary hypertension based on only one higher than normal blood pressure reading. It may take three to six high blood pressure measurements at separate appointments to diagnose secondary hypertension. These measurements may come from home blood pressure monitoring and ambulatory blood pressure monitoring. With ambulatory blood pressure monitoring, a device takes blood pressure measurements automatically at specific times throughout the day.
Your doctor will also want to do tests that check other markers to pinpoint the cause of your high blood pressure. These could include:
- Blood tests. Blood tests are often done to check your levels of potassium, sodium, creatinine, blood glucose, and total cholesterol and triglycerides, among others.
- A urine test (urinalysis). Your doctor may want to check your urine for markers that could show that your high blood pressure is caused by another medical condition.
- Ultrasound of your kidneys. Many kidney conditions are linked to secondary hypertension. In this noninvasive test, a technician moves a small, hand-held device called a transducer over the area to be tested. The transducer sends sound waves into your body, collects the ones that bounce back and sends them to a computer, which creates images of your kidneys.
Electrocardiogram (ECG or EKG). This painless noninvasive test records the electrical signals in your heart. You might have this test if your doctor thinks a heart problem might be causing your secondary hypertension.
In this test, sensors (electrodes) are attached to your chest and sometimes to your limbs. Wires attach the electrodes to a computer. The computer records the heart's electrical signal information and displays it as waves on a monitor or on paper. This test can quickly reveal the timing and duration of each phase in your heartbeat.
Treatment for secondary hypertension involves treating the underlying medical condition with medications or surgery. Once the underlying condition is treated, your blood pressure might decrease or return to normal.
You may need to continue to take blood pressure medication as well, and any underlying medical condition you have may affect your doctor's choice of medication.
Possible drug choices include:
Thiazide diuretics. Diuretics, sometimes called water pills, are medications that help your kidneys eliminate sodium and water. Thiazide diuretics are often the first — but not the only — choice in high blood pressure medications.
Diuretics are often generic and tend to be less expensive than other high blood pressure medications. If you're not taking a diuretic and your blood pressure remains high, talk to your doctor about adding one or replacing a drug you currently take with a diuretic. Possible side effects of diuretics include weakness, leg cramps and a higher risk of sexual dysfunction.
Beta blockers. These medications reduce the workload on your heart and open your blood vessels, causing your heart to beat slower and with less force. When prescribed alone, beta blockers don't work as well in Black people — but they're effective when combined with a thiazide diuretic.
Possible side effects include fatigue, sleep problems, a slowed heart rate, and cold hands and feet. In addition, beta blockers generally aren't prescribed for people with asthma, as they can increase muscle spasms in the lungs.
Angiotensin-converting enzyme (ACE) inhibitors. These medications help relax blood vessels by blocking the formation of a natural chemical that narrows blood vessels. ACE inhibitors may be especially important in treating high blood pressure in people with coronary artery disease, heart failure or kidney failure.
Like beta blockers, ACE inhibitors don't work as well in Black people when prescribed alone, but they're effective when combined with a thiazide diuretic. Possible side effects include dizziness and coughing. ACE inhibitors should not be taken during pregnancy.
Angiotensin II receptor blockers. These medications help relax blood vessels by blocking the action — not the formation — of a natural chemical that narrows blood vessels. Like ACE inhibitors, angiotensin II receptor blockers often are useful for people with coronary artery disease, heart failure or kidney failure.
These medications have fewer potential side effects than do ACE inhibitors. Angiotensin II receptor blockers should not be used during pregnancy.
Calcium channel blockers. These medications help relax the muscles of your blood vessels or slow your heart rate. Calcium channel blockers may work better for some people than ACE inhibitors or beta blockers alone. Possible side effects include water retention, dizziness and constipation.
Grapefruit juice interacts with some calcium channel blockers, increasing levels of the medication in your blood and putting you at a higher risk of side effects. Ask your doctor or pharmacist if your medication is affected by grapefruit juice.
Direct renin inhibitors. These medications relax and widen the arteries by prevention the action of a protein (enzyme) called renin. Renin is released by your kidneys and helps control blood pressure. An example of a direct renin inhibitor is as aliskiren (Tekturna).
Common side effects of aliskiren include dizziness and diarrhea. If you have diabetes or moderate to severe kidney problems, you shouldn't use aliskiren in combination with ACE inhibitors or angiotensin II receptor blockers.
Treatment for secondary hypertension can sometimes be complicated. You may need more than one medication combined with lifestyle changes to control your high blood pressure. Your doctor will want to see you more frequently — possibly as often as once a month — until your blood pressure is controlled. Your doctor may also recommend that you keep track of your blood pressure at home.
Lifestyle and home remedies
Healthy lifestyle changes are recommended to keep your heart healthy and your blood pressure low. These include:
- Eating healthy foods. Try the Dietary Approaches to Stop Hypertension (DASH) diet, which emphasizes fruits, vegetables, whole grains and low-fat dairy foods. Get plenty of potassium, which is found in fruits and vegetables such as potatoes, spinach, bananas and apricots, to help prevent and control high blood pressure. Eat less saturated fat and total fat.
Decreasing the salt in your diet. A lower sodium intake — 1,500 milligrams (mg) a day — is appropriate for people 51 years of age and older and for people of any age who are Black or who have hypertension, diabetes or chronic kidney disease. Otherwise healthy people can aim for 2,300 mg a day or less.
While you can reduce the amount of salt you eat by putting down the saltshaker, you should also pay attention to the amount of salt that's in the processed foods you eat, such as canned soups or frozen dinners.
- Maintaining a healthy weight. If you're overweight, losing even 10 pounds (4.5 kilograms) can lower your blood pressure.
- Increasing physical activity. Regular physical activity can help lower your blood pressure and keep your weight under control. Strive for at least 30 minutes of physical activity a day.
- Limiting alcohol. Even if you're healthy, alcohol can raise your blood pressure. If you choose to drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women and two drinks a day for men.
- Not smoking. Tobacco injures blood vessel walls and speeds up the process of hardening of the arteries. If you smoke, ask your doctor to help you quit.
- Managing stress. Reduce stress as much as possible. Practice healthy coping techniques, such as muscle relaxation and deep breathing. Getting plenty of sleep can help, too.
Preparing for an appointment
Your high blood pressure may be discovered during a routine physical. At that point, your primary care doctor may order more tests or refer you to a doctor who specializes in treating whatever the suspected underlying cause of your high blood pressure may be. For example, if your doctor believes that a kidney problem is causing your high blood pressure, you'll likely be referred to a doctor who specializes in treating kidney disorders (nephrologist).
Because appointments can be brief, and there's often a lot to cover, it's a good idea to arrive well prepared. Here's some information to help you get ready for your appointment and know what to expect from your doctor.
What you can do
- Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as restrict your diet for a certain number of hours before your appointment.
- Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
- Write down key personal information, including any major stresses or recent life changes.
- Make a list of all medications, vitamins or supplements that you're taking, as well as information on the dose you take for each.
- Write down questions to ask your doctor.
Your time with your doctor may be limited, so preparing a list of questions can help you make the most of your time together. For secondary hypertension, some basic questions to ask your doctor include:
- What do you think is causing my high blood pressure?
- What kinds of tests do I need? Do these tests require any special preparation?
- Is my high blood pressure temporary or long lasting?
- What treatments are available for the cause of my high blood pressure and which do you recommend?
- What types of side effects can I expect from treatment?
- I have other health conditions. How can I best manage these conditions together?
- Are there any dietary or activity restrictions that I need to follow?
- What types of lifestyle changes can I make on my own that might help lower my blood pressure?
- Is there a generic alternative to the medicine you're prescribing for me?
- How often do I need to come back to have my blood pressure checked?
- Do I need to check my blood pressure at home? If so, how often?
- Which type of blood pressure machine is best? Can you help me learn how to use it correctly?
- Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment.
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:
- Has anyone in your family ever been diagnosed with high blood pressure?
- If yes, do you know if there was an underlying reason for the high blood pressure? For example, does your relative have diabetes or kidney problems?
- Have you experienced any unusual symptoms?
- How much salt is in your diet?
- Has your body weight changed recently?
- If you were ever pregnant, was your blood pressure elevated during pregnancy?
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