Conn Syndrome

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Also known as: Primary Hyperaldosteronism; Primary Aldosteronism; PA

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).

Thumbnail diagram of the adrenal gland

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. 

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.

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.

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