Understanding secondary hypertension

High blood pressure (hypertension) usually results from a combination of factors, including age, genetics, obesity, a high-salt diet, and lack of exercise. But up to 10% of people with high blood pressure have secondary hypertension, which is a byproduct of another condition or disease.

Most of the time, secondary hypertension is caused by problems with the adrenal glands or the arteries supplying the kidneys (see illustration). Diagnosing and treating the underlying condition often improves or even resolves a person’s elevated blood pressure. But how can you tell if you might have one of these uncommon issues?

“There are four main groups of people in whom you might suspect secondary hypertension as a possibility,” says Dr. Randall Zusman, director of the Division of Hypertension at Harvard-affiliated Massachusetts General Hospital. Specifically:

  1. People who develop high blood pressure before age 30
  2. People who have never had high blood pressure but then develop it “out of the blue,” usually after age 70
  3. People who experience a sudden rise in blood pressure following many years of stable hypertension that’s been well controlled with medication
  4. People who have blood pressure above 130/80 mm Hg despite taking four or more medications.
Kidneys and adrenal glandsillustration of kidneys and adrenal glandsMost cases of secondary hypertension involve problems with the adrenal glands or the renal arteries.

Aldosterone overload

The most common cause of secondary hypertension is hyperaldosteronism, in which one or both adrenal glands make too much aldosterone. This hormone raises blood pressure by telling the kidney to hold on to sodium and water and sending it back into the bloodstream, boosting blood volume. One common cause is a benign (noncancerous) growth in one adrenal gland. Another is bilateral adrenal hyperplasia, in which both adrenal glands are working overtime, for unknown reasons.

Hyperaldosteronism is uncommon in younger people (group 1) and more likely in those who are middle-aged with poorly controlled blood pressure (group 4). A low potassium level can be a red flag, but most people with hyperaldosteronism have normal potassium levels, says Dr. Zusman.

Narrowed kidney arteries

Renal artery stenosis, a narrowing of the arteries that supply the kidneys with blood, is another common cause of secondary hypertension. This condition typically stems from a buildup of fatty plaque in artery walls, a problem usually seen in older people. But it can also occur in young women with an inherited condition called fibromuscular dysplasia, which is marked by an overgrowth of muscular tissue in artery walls. As a result, doctors are more likely to suspect renal artery stenosis among people in groups 1, 3, and 4.

Less-common causes of secondary hypertension include Cushing’s syndrome (which results from over-production of the stress hormone cortisol by the adrenal glands or from long-term use of steroid drugs) and thyroid disorders (diseases or growths that affect the thyroid gland’s production of its hormone). Sleep apnea, a disorder in which you to stop breathing for short periods during sleep, can also trigger rises in hormones that raise blood pressure. (For group 2, any of the problems mentioned so far can lead to secondary hypertension).

Resistant hypertension

Secondary hypertension is common among people with so-called resistant hypertension, which includes people in the fourth group, as well as people who take three different blood pressure drugs at their maximum tolerated doses but still have high blood pressure. Over all, about one in four people with resistant hypertension ends up having an identifiable secondary cause.

However, in many people with stubbornly high blood pressure, the contributing cause isn’t a disorder or condition but lifestyle habits, says Dr. Zusman. Often, these people are not taking their medications as prescribed, or they’re consuming too much sodium (which counteracts the effects of many blood pressure drugs). Some are taking other medications or dietary supplements that elevate blood pressure.

But when those habits aren’t to blame, doctors will look for clues to the other secondary causes, which can be revealed by a physical exam and specialized blood or imaging tests.

Remember: high blood pressure has no symptoms, and secondary causes can strike anyone. So have your blood pressure checked at every health care visit, Dr. Zusman says.

Bible verses for today’s meditation and inspiration: Matthew E. McLaren

Rejoice always, pray continually, give thanks in all circumstances; for this is God’s will for you in Christ Jesus. 1 Thessalonians 5:16-18 NIV

The Lord your God is with you, the Mighty Warrior who saves. He will take great delight in you; in his love he will no longer rebuke you, but will rejoice over you with singing. Zephaniah 3:17

Rejoice in the Lord always. I will say it again: Rejoice! Philippians 4:4 NIV

Be joyful in hope, patient in affliction, faithful in prayer. Romans 12:12 NIV

When anxiety was great within me, your consolation brought me joy. Psalm 94:19 NIV

The Lord has done it this very day; let us rejoice today and be glad. Psalm 118:24 NIV

Though the fig tree does not bud and there are no grapes on the vines, though the olive crop fails and the fields produce no food, though there are no sheep in the pen and no cattle in the stalls, yet I will rejoice in the Lord, I will be joyful in God my Savior. Habakkuk 3:17-18 NIV

You make known to me the path of life; you will fill me with joy in your presence, with eternal pleasures at your right hand. Psalm 16:11 NIV

Though you have not seen him, you love him; and even though you do not see him now, you believe in him and are filled with an inexpressible and glorious joy, for you are receiving the end result of your faith, the salvation of your souls. 1 Peter 1:8-9 NIV

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