The Role of Aldosterone, ACTH, and Renin in Water Retention and High Blood Pressure
A frequent cause of high blood pressure and water retention is when levels of certain hormones in the body are unbalanced or functioning poorly. The hormones that are frequently at fault are secreted by the kidneys and the pituitary or adrenal glands. They are called aldosterone, ACTH, and renin
What is aldosterone?
Aldosterone (ALD) is one of a group of connected hormones. They form the renin–angiotensin–aldosterone system (1); this system is activated when there is a decrease in blood flow to your kidneys following a drop in blood volume or blood pressure such as during heavy bleeding, or sodium levels fall below healthy levels (1).
Aldosterone is a mineralocorticoid, which means that it adjusts the mineral levels in our cells, particularly sodium and potassium (2). It regulates both fluid levels and blood pressure in the body. Stress is a factor that can increase the release of aldosterone and cause sodium levels to rise. Regardless why, an increase in aldosterone results in edema (water retention) and high blood pressure (3).
Someone experiencing high aldosterone levels may also experience (4):
- Low potassium levels (causing muscle cramps)
- Abnormally increased blood volume
- Unusually alkaline blood (because aldosterone promotes acid secretion)
People experiencing high blood pressure and edema may be advised to check their aldosterone level with an aldosterone (ALD) test. When the level of this hormone is too high, it can cause damage to the cardiovascular system. If levels are too high, medicines can be prescribed that will lower aldosterone to healthy levels.
The ALD test
An ALD test is frequently used to diagnose both fluid and electrolyte disorders (5) that may be caused by:
- Adrenal disease
- Heart problems
- Kidney failure
An ALD test may help diagnose problems like (6):
- Over-secretion of aldosterone
- Underactive adrenal glands (adrenal insufficiency)
- Low blood pressure caused by standing up (orthostatic hypotension)
- Hard to control high blood pressure or high blood pressure that occurs at a young age
Renin is also called angiotensinogenase; it’s an enzyme produced by the kidneys to control aldosterone production (7). It’s also essential in the renin–angiotensin aldosterone system (RAAS) which maintains your body’s fluid balance and blood pressure. This system regulates blood plasma volume, lymph and interstitial fluid (the fluid which surrounds the cells in the body) and controls constriction of the arteries and blood vessels (7).
Three factors stimulate the secretion of renin (8):
- When a drop in arterial blood pressure is detected by pressure-sensitive receptors in the arteries
- When a drop in salt level is detected in the kidneys
- When activity is detected in the sympathetic nervous system activity
Renin’s primary function is to increase blood pressure to maintain healthy blood flow to the kidneys. It’s secreted by specialized kidney cells that can detect changes in blood pressure through stretch receptors in the vascular walls (8). Renin starts a chain reaction that makes the hormone called angiotensin, which makes small blood vessels narrower and stimulates the adrenal glands to secrete aldosterone. Aldosterone signals the kidneys to hold on to fluid and salt. Both can increase blood pressure. When this process is out of balance, blood pressure can rise to dangerous levels.
Hypertension and the renin test
If you experience high blood pressure (hypertension), your doctor needs to find out the reason why to prescribe the correct treatment. A renin test is used to discover what’s happening in the body that may be causing it. The doctor might order this kind of test if high blood pressure starts when you’re young or medication hasn’t kept it under control. Because renin is involved in aldosterone metabolism, an ALD test may be conducted at the same time (9).
Your test results will tell the doctor if your renin levels are high, low, or healthy. Either high or low levels could help explain why your blood pressure is too high.
- Excess renin with normal aldosterone levels could mean that you’re salt-sensitive
- Low renin and excess aldosterone may indicate that your adrenal glands aren’t functioning properly
- If both renin and ALD are high, it may be a sign of kidney trouble
Whatever the results are, they will help the doctor decide which drugs or treatments are best to get your blood pressure under control.
Adrenal Corticotropic Hormone (ACTH)
Adrenocorticotropic hormone is a hormone secreted in the anterior (front) pituitary gland in your brain (12).
The role of ACTH is to maintain appropriate levels of the stress hormone cortisol, which is released by the adrenal glands. Cortisol is our body’s natural alarm system. As our body’s primary stress hormone, it works with different parts of the brain to influence our fear, mood, and motivation (13).
Cortisol is best known for fueling the body’s “fight-or-flight” response in a crisis. But, cortisol also has a critical role in a variety of things the body does, like (13):
- Controlling the sleeping and waking cycle
- Boosting energy levels to better handle stress (and restore normal levels afterward)
- Influences how the body uses carbs, proteins, and fats
- Reducing inflammation
- Regulating blood pressure
- Increasing blood sugar
Symptoms of high cortisol can include; high blood pressure, obesity, high blood sugar levels, and edema. Low cortisol levels can cause weight loss, fatigue, low blood pressure, and muscle weakness (14).
The ACTH test
If you’re experiencing the symptoms of a cortisol imbalance, your doctor may order an ACTH test to measure the levels of both ACTH and cortisol in the blood (15). The ACTH test will help your doctor detect the diseases that are associated with too much or too little cortisol in the body (15). Your doctor might also perform a physical examination before making a firm diagnosis.
If it’s determined that an ACTH secreting tumor (sometimes located on an adrenal gland) is the cause of your cortisol imbalance, then surgery may be indicated (16). You may also be prescribed a drug like cabergoline to normalize your cortisol levels (17).
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