Also Known As
Primary Hyperaldosteronism
Primary Aldosteronism
This article was last reviewed on
This article waslast modified on
November 29, 2017.
What is Conn syndrome?

Conn syndrome, also called primary aldosteronism, 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, and electrolyte balance. Its production is normally regulated by renin, an enzyme 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.

With Conn syndrome, excessive aldosterone is produced by one or 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. In Conn syndrome, aldosterone is produced despite low renin levels. 

Secondary aldosteronism must be distinguished from primary aldosteronism. Secondary aldosteronism is not the same as Conn syndrome 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 is the narrowing of blood vessels that supply the kidney, termed renal artery stenosis. Other causes of secondary aldosteronism include congestive heart failure, cirrhosis, kidney disease, and toxemia of pregnancy.

Accordion Title
About Conn syndrome (Primary Aldosteronism)
  • Signs and Symptoms

    Regardless of the cause, increased aldosterone can lead to low blood potassium (hypokalemia), increased blood pH (alkalosis), hypertension and, rarely, to hypernatremia. Conn syndrome may cause few, nonspecific symptoms. The symptoms of people with significant hypokalemia and/or hypertension may include: frequent urination, increased thirst, weakness, fatigue, temporary paralysis, visual disturbances, palpitations, headaches, muscle cramps, and tingling. A doctor may suspect Conn syndrome in a patient who is resistant to standard therapies for hypertension. Diagnosing Conn syndrome is important because it represents one of the few causes of hypertension that is potentially curable.

  • Tests

    The goals of testing for Conn syndrome are to identify primary aldosteronism, distinguish between primary and secondary aldosteronism, and distinguish between those causes of Conn syndrome that may benefit from surgical intervention and those that will usually not.

    Laboratory Tests

    • Electrolytes may be measured to look for an electrolyte imbalance, primarily decreased potassium and chloride along with increased carbon dioxide.
    • Doctors will frequently order blood renin tests along with blood and/or 24-hour urine aldosterone tests to help diagnose primary aldosteronism and to monitor the effectiveness of treatment. The ratio of aldosterone to renin (ARR) is used to test for 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. Based on the results of these tests, a doctor may do a suppression test, using sodium chloride or captopril administration, to see if aldosterone secretion decreases.

    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. 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 doctor 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.

    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 Conn syndrome 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; however, in other cases, additional treatment will be necessary to 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. Treatment with a drug such as spironolactone to block the action of aldosterone and with one or more blood pressure drug therapies may be indicated.

    Those affected by Conn syndrome should consult with their doctors 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.

View Sources

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

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