What is it?

Conn’s syndrome is another name for primary hyperaldosteronism, which is the most common cause of secondary hypertension (high blood pressure) and may also be referred to as aldosteronism. It is a condition characterised by the excess secretion of aldosterone from the cortex – the outer layer – of the adrenal glands. 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 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. When renin increases (due to low blood pressure, decreased blood flow to the kidneys or to a sodium deficiency), aldosterone increases; when renin decreases, aldosterone decreases.

With Conn’s syndrome, excessive amounts of aldosterone are produced by one or more adrenal tumours (usually benign), by hyperplasia, for unknown reasons (idiopathic), or rarely, due to a cancerous adrenal tumour. The regulating action of renin is lost and aldosterone production continues despite suppression of renin levels. Regardless of the cause, increased aldosterone can most commonly lead to hypokalaemia, increased blood pH (alkalosis), and high blood pressure.

Somewhat less frequently, increased aldosterone will lead to polyuria (frequent urination), increased thirst, weakness, temporary paralysis, headaches, muscle cramps, and tingling.

Very rarely, increased aldosterone will lead to hypernatraemia.

The presence of hypokalaemia in a person with high blood pressure suggests the need to look for primary hyperaldosteronism although the most common cause of this pattern is as a side-effect of some of the drugs used to treat high blood pressure.

Diagnosing Conn’s syndrome is important because it represents one of the few causes of high blood pressure that is potentially curable. Although anyone can get primary hyperaldosteronism, it commonly occurs in adults between the ages of 30 and 50 and is more common in women than men. It can sometimes be difficult to diagnose as patients may have variable symptoms or no symptoms at all. Suspicion of Conn’s syndrome may be raised in patients who are resistant to the standard therapies used to treat high blood pressure.

Secondary aldosteronism, which is not considered Conn’s syndrome, can occur as a result of anything that increases renin levels, such as decreased blood flow to the kidneys, low blood pressure, or low sodium levels in the urine. The most important cause is narrowing of the blood vessels that supply the kidney, termed renal artery stenosis. Other causes of secondary hyperaldosteronism include congestive heart failure, cirrhosis, kidney disease, and toxaemia of pregnancy.


Last Review Date: September 6, 2011