Aldosterone | Definition, Composition & Functions

Aldosterone | Definition, Composition & Functions

What is Aldosterone?

Aldosterone (C21H28O5) is a mineralocorticoid (corticosteroid hormone) produced in the adrenal cortex. It handles the regulation of water and electrolyte balance. Aldosterone is a steroid hormone produced in the adrenal cortex and is primarily responsible for regulating blood pressure. It helps the body keep salt and water by stimulating kidney cells to reabsorb sodium. Aldosterone is also responsible for promoting potassium excretion in urine. This hormone is essential for regular brain activity, bone growth, and blood pressure.

Where is Aldosterone made?

Angiotensin II also stimulates this hormone synthesis and secretion. Over 85% of aldosterone is synthesized and secreted in the zona glomerulosa cells of the adrenal cortex, with only 2-5% being synthesized in tooihe zona fasciculata and less than 1% from the zona reticularis. In response to increased blood pressure, angiotensin II activates 10-hydroxysteroid dehydrogenase type 2 (10-HSD2) expression, which produces pregnancy from progesterone. Pregnenolone then gets converted to aldosterone by three beta HSD. Aldosterone synthesis requires a sodium environment found in the renal.

Zona glomerulosa cells of the adrenal cortex form Aldosterone Hormone. The synthesis occurs within specific cells, characteristically arranged around small vessels called zone glomerular. Zone glomerular is the highly vascularized region, which allows excessive aldosterone production.

The conversion of cholesterol into steroid hormones takes place within mitochondria. The pituitary gland regulates aldosterone synthesis by secreting adrenocorticotropic hormone (ACTH). ACTH stimulates both functions, such as synthesis and secretion.

What does Aldosterone do?

Secreted in large amounts by zona glomerulosa cells, Aldosterone is essential for regulating water and electrolyte balance. It also plays other vital roles, such as sodium ion reabsorption in renal tubules, helping maintain normal blood pressure, kidney function, calcium balance, potassium level within body fluids. Finally, it assists with the activation of vitamin D, which is necessary for bone growth. Functions of Aldosterone are described below:

1. Reabsorption in Kidney 

It is a steroid hormone, but it’s also a mineralocorticoid. It can stimulate the kidney cells to reabsorb sodium and water for potassium and hydrogen ions by using a receptor (potassium channel) on the basolateral surface of the epithelial cells in the distal convoluted tubule (DCT) of the renal nephron. A higher potassium concentration inside intercellular space in DCT stimulates cation channels and generates an outward current to maintain electroneutrality and prevent any change in membrane potential or electrochemical gradient across the plasma membrane. This returns excess potassium to the extracellular fluid by increasing its excretion in urine (exchange).

The function of aldosterone depends on potassium and sodium in the blood. The functions depend on two factors:

[1] Plasma [Potassium] level > 5.0 mEq/L AND

[2] Plasma [Sodium] <140 mEq/L.

If both conditions are attained, then aldosterone synthesis is stimulated and released by zona glomerulosa cells into the bloodstream for increasing water and salt excretion while decreasing reabsorption back into renal tubules. Besides that, Aldosterone also influences other endocrine glands, exocrine glands that secrete their substances through ducts into their surrounding body tissues or cavities.

Aldosterone is also responsible for regulating blood pressure indirectly by influencing the fluid volume of plasma and sodium concentration. This hormone will stimulate vasoconstriction, which will increase blood pressure. Vasoconstriction is a narrowing of blood vessels that occurs when the smooth muscle cells in their walls contract to reduce vessel diameter, thus increasing resistance against blood flow through it. Aldosterone has other functions, such as bone development and brain function.

2. Effects on Bone Development:

Aldosterone stimulates osteoblasts (bone-forming cells) to synthesize heregulin, a potent mitogen for osteoclasts (bone-degrading cells). Therefore, it plays a vital role in building up long bones during childhood.

3. Aldosterone in the RAAS

The renin-angiotensin system (RAS) regulates aldosterone production. The primary function of the RAS is to maintain normal blood pressure and to prevent excessive fluid loss from the body. Aldosterone acts through a membrane receptor – mineralocorticoid receptor, which explicitly binds aldosterone. This hormone can have harmful effects if levels are too high or low in the body. High Aldo levels cause heart failure, kidney disease, and low Aldo level causes hypertension.

The renin-angiotensin system (RAS) triggers the production of this hormone. It helps to regulate blood pressure, potassium excretion, and sodium reabsorption. Aldosterone functions with angiotensin II, an enzyme produced by the lungs when it detects low blood pressure via the kidneys. Angiotensin II causes many responses to maintain normal blood pressure, including stimulating aldosterone production in one’s adrenal glands.

Aldosterone also regulates kidney function by controlling electrolytes such as sodium and potassium levels in the body. Someone mainly found the hormone in our kidney tissues and produced in our adrenal cortexes. Because of its location within both organs, it can stimulate the reabsorption of sodium ions within the loop of Henle. This process helps to increase blood volume and clotting factors. In addition, aldosterone releases potassium into our urine through epithelial sodium channels in our distal convoluted tubules. As a result, we can balance electrolytes levels while creating urine necessary for eliminating waste from the body.

4. Influence Sympathetic Nervous System 

Aldosterone also influences other parts of your body, like the brain, lung, heart, and blood vessels. It helps to stimulate the sympathetic nervous system through norepinephrine release. This effect promotes the excretion of sodium in our urine and potassium into our feces via urine while it increases blood vessel diameter for faster circulation.

The hormone also stimulates the heart to beat faster, enhancing circulation while enabling better delivery of oxygen and nutrients. The increased blood flow can also take away harmful byproducts like lactic acid and assist with wound healing within your body. Last, it causes your lungs to hyper aldosterone-breath eonism when small tumors faster maintain the oxygen levels within our bloodstream.

Blood Pressure Medication

As a treatment for high blood pressure, doctors might recommend taking medications called ACE inhibitors. These drugs act on the system to block angiotensin II production, which can lower excess water and sodium back into your bloodstream. It also works by blocking the binding of angiotensin II to its receptor within cells. Since angiotensin II normally stimulates the secretion of aldosterone from the adrenal cortex, the dampened signal helps reduce levels of this hormone in your system.

Spironolactone

Doctors might also prescribe this medication if your body produces excess aldosterone. It works by blocking the effects of aldosterone receptors in target cells, which can have an anti-hypertensive effect on blood pressure when taken alone or when used with other drugs that lower high blood pressure.

ACE Inhibitors 

Angiotensin-converting enzyme (ACE) inhibitors, sometimes referred to as “water pills,” work by lowering blood pressure in different ways. For example, ACE inhibitors prevent the body’s

Angiotensin II Receptor Blocker

Production of angiotensin II, can lead to a drop in systolic and diastolic blood pressure. Other drugs in this class can block receptors that bind with angiotensin II once it is produced, thus preventing its effects on the heart and arteries.

Known as an ARB, this drug works by stopping the hormone angiotensin II from binding to nerve cells and blood vessel walls. This ultimately reduces pressure on the arteries and veins throughout the body. However, these medications don’t affect aldosterone levels, so they aren’t recommended for patients with high potassium or low renin levels.

Diuretics  

These medications help reduce blood volume and pressure by increasing the amount of water excreted by your kidneys. They also inhibit aldosterone production within the adrenal glands so that less sodium is reabsorbed back into your body, causing fluid levels to decrease. However, if you have heart failure or liver disease, diuretics may not be appropriate for you.

Potassium-Sparing Diuretic

This type of diuretic decreases your body’s production of aldosterone, which in turn reduces the amount of potassium excreted through urine. Therefore, these medications are not recommended for low blood pressure or heart failure patients. Instead, they block potassium channels to leave more sodium via urine while your body keeps the necessary amounts needed to maintain healthy tissue function.

Vasodilators  

These medications relax and widen blood vessels throughout the body by slowing down the heart rate. Reducing resistance reduces strain on your heart, which lowers both systolic and diastolic blood pressure levels. They also help open up arteries to accommodate more blood flow. However, these medications cannot be used alone and must be combined with other therapies, such as diet and exercise.

Aldosterone Antagonist

This medication works by blocking aldosterone from binding with receptor sites in the kidney. By doing this, less sodium is reabsorbed back into the body through urine output, thus causing fluid volume to decrease and lower elevated blood pressure levels caused by aldosterone overproduction.

Natural Treatment

Although the excessive secretion of aldosterone is treated through medical intervention, there are some natural ways to manage your high blood pressure.

Although dietary changes can be an effective way to fight this condition, it’s essential to consult a physician before starting any new diet since certain foods affect our bodies differently. Some of these foods include:

Foods to avoid:

Salt, Sugar, alcohol, coffee, and chocolate. Increased potassium intake through fruits and vegetables like bananas, oranges, or broccoli could help reduce its levels. Decreasing sodium sources from processed food will also help block sodium reabsorption induced by its production in the kidneys.

Eat Foods Rich in Flavonoids:

The Department of Medicine did one study, Division of Cardiology at Boston University School of Medicine, found that “the risk factors for heart disease include an increased dietary intake of sodium and a decreased dietary intake of flavonoid-rich foods. Increased intake of fruits and vegetables rich in quercetin (such as onions) might help reduce high blood pressure levels while maintaining low blood pressure levels.” Other foods containing flavonoids are green tea, blueberries, cherries, apples, cranberries, and red grapes.

Talking to your doctor about adding some exercise into your daily routine can also be effective when lowering your blood pressure naturally. Depending on how active you are already, you might want to try walking for about 20 minutes per day. This can help authenticate the reduction in your blood pressure while strengthening your heart at the same time. If you can’t walk daily, try doing some weight training or light calisthenic exercises.