What Is Treatment-Resistant Hypertension?

Causes of Treatment-Resistant Hypertension

When several medications fail to bring down your blood pressure, your care team looks for factors that could be contributing, says Payal Kohli, MD, a cardiologist in private practice in Aurora, Colorado, and an associate adjunct professor of medicine at Johns Hopkins University Ciccarone Center for the Prevention of Cardiovascular Disease in Baltimore and Duke University in Durham, North Carolina.

“Finding and treating those causes can often make blood pressure much easier to control,” Dr. Kohli says. These causes can include factors such as other medical conditions or dietary choices.

Primary Aldosteronism

The adrenal glands make a hormone called aldosterone, which helps control how much sodium and water the kidneys retain.

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In primary aldosteronism, the adrenal glands produce too much aldosterone.

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The kidneys then hold onto extra sodium and water, increasing the amount of fluid in the blood vessels and raising blood pressure, explains Shaista Malik, MD, PhD, MPH, a cardiologist at the University of California Irvine Health Susan Samueli Integrative Health Institute and a professor of medicine in the division of cardiology at UC Irvine School of Medicine.

Obstructive Sleep Apnea

Obstructive sleep apnea causes the airway to repeatedly narrow or close during sleep, briefly interrupting breathing.

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Each interruption can lower oxygen levels and activate the body’s fight-or-flight response, which tightens blood vessels and raises blood pressure.

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Repeated sleep apnea episodes can make blood pressure more difficult to control.

Chronic Kidney Disease

Healthy kidneys remove extra water and waste from the body through urine.

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With kidney disease, fluid can build up in the blood vessels, leading to high blood pressure.

The relationship goes both ways. High blood pressure can also damage the kidneys, which can contribute to even higher blood pressure.

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Narrowed Kidney Arteries

The kidneys receive blood through vessels called renal arteries.

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If these arteries narrow (a condition called renal artery stenosis), less blood reaches the kidneys. Plaque buildup inside the arteries is one possible cause of renal artery stenosis, Basman says.

In response to reduced blood flow, the kidneys activate a hormone system that makes the body retain salt and water and tightens blood vessels.

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Both effects can raise blood pressure.

Other Hormone Disorders

Other conditions involving the thyroid or adrenal glands can also raise blood pressure.

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An overactive or underactive thyroid can affect blood pressure.

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Less common causes include Cushing’s syndrome and pheochromocytoma, Basman says. In Cushing syndrome, the body makes too much cortisol (known as the stress hormone).

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Pheochromocytoma is a rare adrenal tumor that releases excess fight-or-flight hormones, such as adrenaline.

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Medications and Supplements

Birth control pills can also raise blood pressure, especially those with higher doses of estrogen.

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Stimulants used to treat attention deficit hyperactivity disorder (ADHD), such as methylphenidate (Ritalin), can have a similar effect.

Other contributors to high blood pressure include decongestants and certain supplements or herbal products, including licorice root, bitter orange, and yohimbine, Dr. Malik notes.