Aldosterone, Hyperaldosteronism and Hypoaldosteronism
What is Aldosterone?
Aldosterone is a hormone made by the adrenal glands. When it's released into the bloodstream, it increases the sodium level in the blood and decreases the potassium level. These changes cause blood volume and blood pressure to increase.
The amount of aldosterone that enters the blood changes as internal conditions in the body change. The hormone adjusts blood volume and blood pressure as necessary to help our body function properly.
Hyperaldosteronism is a disorder in which too much aldosterone is made. The excess hormone causes the blood pressure to increase beyond a healthy level. In hypoaldosteronism, not enough aldosterone is made, which results in a blood pressure that is too low.
The outer layer of the adrenal gland is called the cortex and the inner layer is called the medulla. Each layer secretes different chemicals, as shown in the diagram above.
Aldosterone and the Kidneys
There are two adrenal glands, one on top of each kidney. The right adrenal gland (from the owner's point of view) has a triangular shape. The left one is shaped like a half-moon. Aldosterone is made by the outer layer of the adrenal glands, which is known as the adrenal cortex.
Sodium Ion Reabsorption
Sodium ions are filtered out of the blood and into the kidney tubules (nephrons). If the ions stay in the nephrons, they are transported to the urinary bladder and released from the body in urine. Some sodium ions are reabsorbed into the blood vessels around the nephrons and don't reach the urinary bladder, however. One function of aldosterone is to increase sodium ion reabsorption from the nephrons.
Whenever sodium ions are reabsorbed into the bloodstream, the absorption of water molecules follows. The water increases the volume of the blood, which in turn increases blood pressure. Therefore aldosterone indirectly increases both blood volume and blood pressure.
Potassium Ion Excretion
Aldosterone also regulates the concentration of potassium ions in the blood. As sodium ions are reabsorbed into the blood vessels around the nephron, potassium ions are transported in the opposite direction - from the blood vessels into the nephron - and are then excreted in the urine. Aldosterone increases this transport and excretion of potassium ions.
Summary of Aldosterone's Effects
Concentration of sodium ions in blood - UP
Blood pressure - UP
Concentration of potassium ions in blood - DOWN
In human biology, the prefix hyper means that something is in excess. Hyperaldosteronism means that the aldosterone level in the blood is too high, for example. The prefix hypo means that the amount of something is too low. For example, people with hypoaldosteronism don't have enough aldosterone in their blood.
Hyperaldosteronism is an abnormally high level of aldosterone in the body. It can arise due to a problem within the adrenal glands (primary hyperaldosteronism) or to a problem which originates outside the adrenal glands (secondary hyperaldosteronism).
Primary hyperaldosteronism is also called Conn's syndrome. It's often caused by a tumor in one of the adrenal glands. The tumor is usually an adenoma and is benign, meaning that it stays in one place and is non-cancerous. Sometimes the name "Conn's syndrome" is reserved for primary hyperaldosteronism produced by an adenoma. Rarely, the condition is caused by a cancerous tumor in an adrenal gland.
Primary hyperaldosteronism may also develop due to idiopathic adrenal hyperplasia. “Hyperplasia” means increased cell production, which causes enlargement of an organ or gland, and “idiopathic” means that there is no known cause for the change. Generally both the adrenal glands undergo hyperplasia.
It was once thought that Conn's syndrome was a rare disorder. Now doctors are beginning to think that it is more common than previously believed and is responsible for some cases of hypertension (high blood pressure). The condition is most common in adults than children. There is a rare inherited form of the disorder called familial hyperaldosteronism which may appear in childhood, however.
Conn's Syndrome or Primary Hyperaldosteronism
Secondary hyperaldosteronism is caused by a factor outside the adrenal glands that stimulates the production of aldosterone.
One possible cause of secondary hyperaldosteronism is an increase in renin due to a kidney disorder. Renin is an enzyme that is made by the kidneys. The enzyme is released into the bloodstream when there is low blood pressure caused by low blood volume. It's also released when the concentration of sodium ions in the nephrons is too high and the concentration in the blood is too low.
Renin triggers a series of reactions that stimulate aldosterone release. The aldosterone returns conditions to normal by stimulating sodium ion reabsorption into the body and increasing blood volume (and therefore blood pressure). If too much renin is produced, the level of aldosterone will increase too.
Secondary hyperaldosteronism may also develop as part of some other diseases, such as cirrhosis of the liver and congestive heart failure.
Seek Medical Advice When Necessary
Anyone who has unexplained symptoms resembling those of an aldodesterone problem should visit a doctor. The symptoms listed below can be caused by a variety of health problems. A doctor's expertise is needed for a diagnosis and treatment recommendations.
Symptoms of Hyperaldosteronism
People with too much aldosterone in their bodies often develop high blood pressure. This disorder may cause no additional symptoms. It may produce problems such as headaches, vision problems and an irregular heartbeat, however.
Some patients with hyperaldosteronism develop symptoms of a potassium deficiency. A low potassium level is known as hypokalemia. A mild case of hypokalemia may cause no symptoms. If symptoms do appear, they may include muscle weakness, numbness, tingling and cramps. The patient may also experience an irregular heartbeat. If the disorder lasts for a long time, there may be excessive urine production.
Licorice and Hyperaldosteronism-Like Symptoms
Licorice doesn’t cause hyperaldosteronism, but it can produce similar effects to an increased aldosterone level. True licorice contains a sweet substance called glycyrrhizin, which affects the body in a similar way to aldosterone. It raises the level of sodium ions in the blood, increases blood volume and increases blood pressure. It also lowers the level of potassium ions in the blood.
Most “licorice” bought in candy stores actually contains very little or no licorice and is flavored with other substances, such as anise oil. This is safe to eat as far as changing blood pressure is concerned. However, herbal teas containing licorice, real licorice candies and other products containing licorice root should be used with caution.
A doctor will likely have a variety of treatments to offer someone with hyperaldosteronism. An adrenal gland tumor may be surgically removed. Drugs may be given to block the action of excess aldosterone. Potassium supplements may be prescribed for temporary use before the aldosterone level returns to normal. The treatment of other disorders producing the hyperaldosteronism may also return the aldosterone to a normal level.
The hormones released by the adrenal cortex belong to three classes of steroid chemicals: the mineralocorticoids (such as aldosterone), the glucocorticoids (such as cortisol) and the androgens (a group of hormones that produce male characteristics).
A low blood level of aldosterone is known as hypoaldosteronism. Aldosterone deficiency is most often accompanied by a deficiency of other hormones made by the adrenal cortex in a condition called primary adrenal insufficiency, also known as Addison’s disease. In this disorder, the adrenal cortex fails to produce enough of one or more of its hormones. Primary adrenal insufficiency develops due to damage to the adrenal cortex.
There are other possible causes of hypoaldosteronism. Kidney damage may lead to decreased renin production, which may then result in decreased production of aldosterone. NSAIDs (nonsteroidal anti-inflammatory drugs) and certain diuretics have been found to lower the aldosterone level in the blood of some people. Diabetics are more likely to develop hypoaldosteronism than non-diabetics.
Hypoaldosteronism may also be caused by some autoimmune diseases. Our immune system normally attacks bacteria, viruses and other agents that can cause disease. In an autoimmune condition, the immune system mistakenly attacks the body's own tissues.
Aldosterone Action in Detail
Symptoms of Hypoaldosteronism
Possible signs of hypoaldosteronism include a high blood potassium level (hyperkalemia), low blood sodium level and low blood pressure. Each of these conditions can produce its own set of symptoms, some of which are listed below. (As in hyperaldosteronism, the symptoms may be caused by other disorders. A doctor should be consulted if the symptoms are present.)
- Hyperkalemia can cause an irregular heartbeat or a slow heart rate, muscle fatigue and weakness.
- A low concentration of sodium ions in the blood is known as hyponatremia. Symptoms can include fatigue, confusion, muscle twitches, weakness, nausea and a headache
- Very low blood pressure can cause symptoms such as dizziness, lightheadedness, fainting (technically known as syncope), blurred vision, nausea and cold, pale skin.
Treatment of hypoaldosteronism includes treating the health problems that are interfering with aldosterone production, replacing medications that are lowering the blood level of the hormone, and the use of mineralocorticoid medications to replace the missing aldosterone.
Aldosterone is a very useful molecule, but it can cause big problems when it is in excess or at an inadequate level. Fortunately, doctors have ways to help most people with these problems.
References and Further Reading
© 2011 Linda Crampton