Low Renin Hypertension - Causes, Symptoms, and Management

Introduction

Low Renin Hypertension (LRH) is a subtype of high blood pressure (Hypertension). Renin is an enzyme that works with other molecules in the body to keep the electrolytes in balance. This condition is always an underdiagnosed cause of hypertension. Some forms of hypertension are associated with low renin levels.

What Is Renin?

Renin is an enzyme released from the cells of the kidney. It helps in the control of blood pressure and maintains the levels of sodium and potassium in the body. It is released in response to low sodium levels or low blood volume. Renin is a component of the Renin-Angiotensin-Aldosterone System (RAAS). It is a chain reaction to regulate blood pressure. Renin controls the hormone aldosterone secreted by the adrenal gland.

What Is the Mechanism Carried Out by the Renin?

Renin mainly regulates blood pressure. It works along with angiotensin and aldosterone. It manages sodium and potassium levels in the body.

• Renin helps convert angiotensinogen (a protein released into the blood by the liver) into angiotensin I (a hormone that narrows the blood vessel).

• Angiotensin I gets converted to angiotensin II.

• Angiotensin II helps in the narrowing of blood vessels and also helps in stimulating the release of aldosterone. This acts on angiotensin receptors.

• Aldosterone helps retain salt and water. Hence, there is an increase in the amount of water in the body. This action increases blood pressure.

What Is Low Renin Hypertension?

Hypertension means high blood pressure. It is considered a dangerous condition because it does not show any symptoms. Hypertension puts the individual at risk of stroke, heart attack, and other problems. Most people need to realize it, and hence, checkups are necessary. Blood pressure may be maintained by adopting good dietary habits, regular exercise, and medication.

Blood Pressure (BP) measures the pressure or force with which the blood pushes against the blood vessel walls. It is measured in terms of Millimeters of Mercury (mmHg). It has two numbers. One being systolic blood pressure and the other being diastolic blood pressure.

• Systolic BP measures the pressure on the artery walls when the heart beats or contracts.

• Diastolic BP is the pressure measured between the heartbeats when the heart rests.

According to the World Health Organization (WHO), 1.2 billion people aged 30 to 79 globally are affected by hypertension. The normal BP is 120/80 mmHg. 120 mmHg (millimeter of mercury) is the reading for systolic BP, and 80 mmHg is for diastolic BP. A change in renin levels, whether low or high, is associated with hypertension.

What Are the Causes of Low Renin Hypertension?

According to the work of RAAS, when there is a high level of renin, the BP increases. In the case of LRH, high BP is observed even though there is a low level of renin or typical renin levels. There may not be sufficient renin to control the process that helps regulate the BP.

• Causes may be based on subtype.

• Inherited genetic syndromes.

• Acquired genetic mutations.

• Environmental factors.

Aldosterone levels are to be checked to determine the exact cause of LRH.

• When there is low renin but high aldosterone levels, it may lead to primary aldosteronism. It is also called hyperaldosteronism or Conn’s Syndrome (a condition in which too much aldosterone is made by the adrenal gland). This is the most common cause of LRH.

• Sometimes, benign or small tumors on the adrenal gland may cause hyperaldosteronism.

• If renin levels are low and aldosterone levels are normal or standard, the cause is Low Renin Essential Hypertension (LREH). This type of hypertension is primary, which means no other health conditions are responsible for this hypertension.

• If both renin and aldosterone levels are low, many causes may be divided into acquired and genetic causes.

Acquired causes include:

• Cushing syndrome (high cortisol level exposure).

• Acute health issues.

• High intake of salt.

• Diabetic kidney disease.

• Use of some medications.

• More eating of black licorice.

Genetic causes include:

• Liddle Syndrome (a condition characterized by hyporeninemia, hypertension with hypokalemic metabolic alkalosis, and suppressed aldosterone secretion).

• Mineralocorticoid receptor activating mutation.

• Apparent mineralocorticoid excess syndrome.

• Congenital adrenal hyperplasia (a genetic disorder of adrenal glands suppressing hormone production).

• Glucocorticoid resistance.

• Gordon’s syndrome (a condition characterized by .low-renin hypertension associated with hyperkalemia and metabolic acidosis).

What Are the Symptoms Exhibited by Low Renin Hypertension?

Symptoms depend on the cause of low renin hypertension. This can only be detected once the healthcare provider checks the blood tests. It is observed that hypertension itself does not show symptoms unless complications occur. Primary Aldosteronism shows symptoms like:

• Muscle weakness.

• Hypokalemia (low potassium levels).

• Increased thirst.

• Tiredness.

• Heart-related diseases like heart attack, stroke, atrial fibrillation.

How to Diagnose Low Renin Hypertension?

Diagnosis can be done by:

• Medical History: Before making the diagnosis, a healthcare provider asks for symptoms, a family history of hypertension, and any genetic disorders.

• A Blood Test or Urine Test: Levels of renin, aldosterone, potassium, and cortisol are checked.

• Kidney Function Test: This is done to know about vitamin D, red blood cells, and hormones regulating BP.

Some factors that affect the levels of renin are:

• Some medications.

• High intake of salt.

• The first phase of the menstrual cycle.

How to Treat Low Renin Hypertension?

• Low renin hypertension can be treated with medications as well as home-based techniques.

• Depending on the subtype, surgery may be done.

• The main goal of the treatment is to improve RAAS (Renin-Angiotensin-Aldosterone System).

1. Medications:

Diuretics are used in the treatment of high aldosterone levels. Angiotensin II Receptor Blockers (ARBs) or Angiotensin-Converting Enzyme Inhibitors (ACE) prevent blood vessels from narrowing. Calcium channel blockers are used to promote relaxation of blood vessels.

2. Surgery:

In the case of hyperaldosteronism, which is due to tumors in the adrenal glands, surgery is done to remove the tumors, called Adrenalectomy.

3. Home-Based Techniques:

• Reducing sodium intake.

• Managing stress levels.

• Regular exercise.

• Maintaining ideal weight.

• Limiting alcohol consumption.

• Having a good sleep every day.

Conclusion

Low renin hypertension is a common form of hypertension caused by low levels of renin enzymes. This cannot be diagnosed easily as it does not show any symptoms. Hence, knowing about low renin hypertension and its causes, symptoms, and management is important. Knowing helps to seek medical help at the earliest. Early diagnosis leads to effective treatment. This, in turn, helps achieve a good quality of life.