Primary Aldosteronism (Conn Syndrome)

What is primary aldosteronism?

Primary aldosteronism, also sometimes called Conn syndrome, is an endocrine disorder characterized by excessive secretion of the hormone aldosterone from the adrenal glands. This overproduction leads to the retention of sodium and loss of potassium in the body, resulting in high blood pressure (hypertension).

The adrenal glands are small triangular organs located on the top of the kidneys. They are part of the endocrine system, a group of glands that produce and secrete hormones that act on and regulate many systems throughout the body. Aldosterone is produced by the outer layer of the adrenal glands, the cortex. It is a hormone that plays an important role in maintaining blood volume, pressure, pH, and electrolyte balance. Its production is normally regulated by renin, a protein produced in the kidneys. Aldosterone increases when renin increases due to low blood pressure, decreased blood flow to the kidneys, or a sodium deficiency. When renin decreases, aldosterone also decreases.

In primary aldosteronism, an individual can produce excess aldosterone because of one ore more benign adrenal tumors, by overactivity of both glands called bilateral adrenal hyperplasia, or for unknown reasons (idiopathic). Rarely, it is caused by a cancerous (malignant) adrenal tumor. Regardless of the cause, aldosterone is produced despite low renin levels.

Increased aldosterone can lead to increased blood pH (alkalosis), hypertension, and to high blood sodium (hypernatremia). Primary aldosteronism may cause a few nonspecific symptoms such as frequent urination, weakness, fatigue, and muscle cramps. A healthcare practitioner may suspect primary aldosteronism in a person who has high blood pressure that is difficult to control, requires multiple blood pressure medications, and/or does not respond to standard treatments.

Secondary aldosteronism must be distinguished from primary aldosteronism. Secondary aldosteronism is caused by problems outside the adrenal glands that lead to the glands releasing too much aldosterone. It is different from primary aldosteronism because renin levels are high in secondary aldosteronism. Anything that increases renin levels, such as decreased blood flow to the kidneys, low blood pressure, or low sodium levels in the urine, can cause secondary aldosteronism. The most important cause of secondary aldosteronism is the narrowing of blood vessels that supply the kidney, termed renal artery stenosis. Other causes include congestive heart failure, cirrhosis, kidney disease, and toxemia of pregnancy.

About Primary Aldosteronism

Signs and Symptoms
Signs and symptoms of primary aldosteronism can be nonspecific and similar to the symptoms of other conditions. Often the only symptom is mild to moderate high blood pressure. Symptoms are often associated with significant low potassium (hypokalemia) and/or hypertension. They may include:

Frequent urination

Increased thirst

Weakness

Fatigue

Temporary paralysis

Visual disturbances

Palpitations

Headaches

Muscle cramps, which is especially common in people from Asia

Tingling
Tests
The goals of testing for primary aldosteronism are to distinguish it from secondary aldosteronism and to determine the cause.

Laboratory Tests

Electrolytes may be measured to look for an electrolyte imbalance, primarily decreased potassium and chloride along with increased carbon dioxide.

The ratio of aldosterone to renin in the blood (ARR) is the recommended screening test in the Endocrine Society’s 2016 guidelines for detecting primary aldosteronism. If renin levels are low and aldosterone levels are high, then the ratio will be significantly increased and primary aldosteronism is the likely diagnosis. If ARR results are positive, the Endocrine Society recommends following up with a suppression test. These tests use sodium chloride (salt loading) or fludrocortisone, or captopril administration, to see if aldosterone secretion decreases. If it does, then the diagnosis of primary aldosteronism is confirmed.

These tests may be followed by a CT (computed tomography) or MRI (magnetic resonance imaging) scan of the adrenal glands to look for a tumor. The Endocrine Society recommends CT scans for everyone with primary aldosteronism. This process can be complicated as benign adrenal tumors are relatively common, especially as people get older. Many of them do not secrete aldosterone and are found incidentally during procedures performed for other reasons. Determining hyperplasia can also be tricky because the size of normal adrenal glands may vary significantly from one person to the next.

If hyperplasia or an aldosterone-producing tumor is suspected but not easily locatable, then a healthcare practitioner may order adrenal venous sampling. In this procedure, blood is collected from the vein that carries blood away from each adrenal gland. These blood samples are tested for aldosterone (sometimes cortisol is also measured and an aldosterone/cortisol ratio is calculated) and then the results from the two adrenal glands are compared. If they are significantly different, then it is likely that an adenoma is located in the gland with the highest aldosterone concentration.

Rarely, primary aldosteronism may be familial, due to mutations that enhance aldosterone production.

Non-Laboratory Tests

Blood pressure measurement – often the first indicator of possible primary aldosteronism

CT (computed tomography) scan or MRI (magnetic resonance imaging) – used to detect adrenal tumors
Treatment

The goals of treating primary aldosteronism are to lower blood pressure to normal or near normal levels, decrease blood aldosterone levels, and resolve any electrolyte imbalances. The type(s) of treatment depends on the cause of the excess aldosterone secretion.

If it is due to a single benign adrenal tumor, then the affected gland may be surgically removed. In many cases, this will completely resolve hypertension and other associated symptoms. In other cases, additional treatment will be necessary to block aldosterone, manage fluid build-up, and fully control blood pressure.

If the primary aldosteronism is due to a cancerous tumor, which is rare, then organs located next to the affected adrenal gland will need to be evaluated during surgery and more than the adrenal gland may need to be removed.

If the cause of the primary aldosteronism cannot be determined (idiopathic) or appears to be due to hyperplasia in both adrenal glands, then surgery is usually not recommended since surgery only cures a minority of these cases. Treatment may include a drug such as spironolactone to block the action of aldosterone and one or more blood pressure drug therapies instead.

Those affected by primary aldosteronism should consult with their healthcare provider and, when indicated, with an endocrinologist (a specialist in the endocrine system). Treatment for primary aldosteronism must often be adjusted to accommodate underlying hypertension, kidney disease, congestive heart failure, and a variety of other disorders. Lifestyle changes, such as dietary changes and exercise, may improve response to hypertension medications.

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Sources Used in Current Review

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