Low renin hypertension (LRH) is a subtype of high blood pressure. It describes hypertension with low levels of an enzyme called renin.
Renin works with other molecules in the body to keep your electrolytes in balance. Having low renin levels could mean that your body has too much sodium or that you have salt-sensitive hypertension.
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Diagnosing LRH is important in determining the best course of treatment for your high blood pressure. But your doctor will also want to check for other factors.
Hypertension and the RAAS
To understand LRH, you first need to understand the renin-angiotensin-aldosterone system (RAAS).
- Renin is an enzyme made in the kidneys. It starts the whole process.
- Angiotensinogen, a protein produced by the liver, is broken down by renin to form angiotensin I.
- Another enzyme converts angiotensin I to angiotensin II, a protein hormone that can narrow your blood vessels to increase your blood pressure.
- Angiotensin II causes the adrenal glands above your kidneys to release aldosterone, another hormone. Aldosterone helps to manage the amount of salt in your blood.
Collectively, the RAAS is responsible for controlling your blood volume, along with sodium and potassium levels that regulate your blood pressure.
When the RAAS works as expected, high levels of renin increase your blood pressure. But with LRH, you experience high blood pressure even with low or typical renin levels. You may not have enough renin to help set off the processes that control your blood pressure.
Causes of LRH vary based on subtype. This
- inherited genetic syndromes
- acquired genetic mutations
- environmental factors
To determine the exact cause of your LRH, your doctor will consider your aldosterone level. The level of aldosterone in your blood can narrow down a search for the cause of your LRH.
High aldosterone levels
If your renin levels are low, but your aldosterone levels are high, you may have primary aldosteronism. It‘s also called hyperaldosteronism or Conn‘s syndrome.
Primary aldosteronism is the most common cause of LRH. A 2018 study indicates that it affects an estimated
According to the same 2018 study, it can sometimes run in families. An uncommon inherited gene mutation can cause familial hyperaldosteronism.
In some cases, small but benign (noncancerous) tumors on the adrenal glands can also cause hyperaldosteronism.
Standard aldosterone levels
If your renin levels are low while your aldosterone levels are standard, the most likely cause is low renin essential hypertension (LREH). This is a form of primary or essential hypertension, meaning that no other health condition is responsible for your high blood pressure.
LREH may also be diagnosed in cases of low or high aldosterone when other causes are ruled out.
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Low aldosterone levels
If your renin and aldosterone levels are both low,
- Cushing syndrome, from elevated steroid levels
- acute illnesses
- high salt intake
- diabetic kidney disease
- use of certain medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs)
- eating a lot of black licorice
Genetic causes include:
- Liddle syndrome. Liddle syndrome is a rare genetic disorder that causes high blood pressure due to atypical kidney function.
- Mineralocorticoid receptor (MR) activating mutation. This is a genetic disorder that may interfere with your body‘s ability to regulate electrolytes. This leads to an inability to regulate your blood pressure.
- Apparent mineralocorticoid excess (AME) syndrome. A
2018 studysuggested that AME syndrome, which is a rare disease, is primarily linked to LRH in children.
- Congenital adrenal hyperplasia (CAH).
CAHis a rare inherited disorder that interferes with adrenal gland function.
- Glucocorticoid resistance (Chrousos syndrome).
Glucocorticoid resistanceis a rare genetic condition that causes an insensitivity to glucocorticoids. This can lead to hypertension.
- Gordon‘s syndrome. Gordon‘s syndrome is a rare genetic condition that may cause hypertension and high potassium levels.
Because some of the genetic causes of LRH have a wide variety of symptoms, they may not always result in high blood pressure.
For example, CAH is a family of disorders with classical and nonclassical forms. According to the Children‘s Hospital of Philadelphia, its classical form usually presents with low blood pressure.
The symptoms of LRH depend on the underlying cause. But you may not know you have it until your doctor orders blood tests and sees the results.
Aside from high blood pressure, primary aldosteronism is usually associated with muscle weakness and low potassium levels in your blood (hypokalemia). This can cause increased thirst, cramps, and weakness.
People with LRH due to primary aldosteronism are also at higher risk of cardiovascular issues, according to a
Before making an LRH diagnosis, your doctor will ask you about any symptoms you’re experiencing, as well as your personal and family history of hypertension. They may also ask you about any genetic disorders that run in your family.
Diagnosing LRH requires blood or urine testing. Your doctor will be looking for levels of:
- renin, with typical levels ranging from 1.9 to 3.7 nanograms per milliliter per hour (ng/ml/hour) according to the University of California, Los Angeles
- aldosterone, to determine the subtype
- potassium, to check for hypokalemia
- cortisol, to check for steroid production by the adrenal glands
Your doctor may also perform a kidney function test.
In some cases, doctors won‘t know the exact cause of your LRH until they see how you respond to medication.
Certain factors may affect your renin levels. Your doctor will consider these when evaluating your results. One
- taking certain medications
- high salt intake
- first (follicular) phase of the menstrual cycle
Your doctor might recommend genetic counseling if certain conditions run in your family that can be linked to hypertension.
You can treat your LRH with a combination of medications and home management techniques. Depending on the subtype, you may also need surgery. The overall goal of treatment is to improve the RAAS while also lowering your blood pressure.
- diuretics such as spironolactone or eplerenone, which may be used to treat high aldosterone levels
- angiotensin II receptor blockers (ARBs) or angiotensin-converting enzyme (ACE) inhibitors to prevent your blood vessels from narrowing
- calcium channel blockers to promote blood vessel relaxation
To help treat hyperaldosteronism caused by tumors, doctors may recommend adrenalectomy. In this procedure, surgeons remove the tumors on your adrenal glands.
Results may vary. However, the Society for Endocrinology estimates that surgery may help reduce blood pressure in over 70 percent of participants with primary hyperaldosteronism. Some people may also have a reduced need for their blood pressure medications.
Reducing your sodium intake could offset high blood sodium levels in LRH. It may also be helpful if you have salt-sensitive hypertension. To help you make dietary changes, your doctor may recommend the Dietary Approaches to Stop Hypertension (DASH) eating plan.
- whole grains
The DASH diet also permits low fat poultry, fish, and dairy products. Your daily intake of sodium should be 1,500 to 2,300 milligrams per day.
In addition to the DASH diet, your doctor may recommend other home care strategies to help control your blood pressure. The
- managing stress
- quitting smoking
- exercising regularly
- maintaining your ideal weight
- limiting alcohol intake
- getting 7 to 9 hours of sleep every night
LRH is a relatively common hypertension subtype that‘s related to the RAAS. While some cases of low renin are genetic, most are acquired, with the risk increasing with age.
You may not know you have LRH until your doctor orders a blood test. Like other forms of hypertension, LRH also doesn‘t usually cause any noticeable symptoms unless related complications develop.
You can make changes in your diet and lifestyle to help manage LRH. However, depending on the underlying cause, you may require certain medications. Your doctor may also suggest surgery in rare cases.