Conn's Syndrome

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What is it?

Conn’s syndrome is another name for primary hyperaldosteronism and may also be referred to as aldosteronism. The condition was named by Jerome Conn who first described a tumour of the adrenal glands that produced excess aldosterone. It is a disease of the outer layer of the adrenal glands called the adrenal cortex. The adrenal glands are small triangular organs which sit on top of the kidneys. The glands are part of the endocrine system, a group of glands that produce and secrete hormones that act on and regulate many body functions. Aldosterone is a hormone that plays an important role in maintaining blood volume, pressure and the concentration of sodium and other electrolytes. The amount of aldosterone produced is normally regulated by renin, an enzyme made in the kidneys. When renin levels increase due to low blood pressure, reduced flow of blood to the kidneys or to sodium deficiency, aldosterone increases and when renin decreases, aldosterone decreases.

In Conn’s syndrome, very large amounts of aldosterone are produced by one or more adrenal tumours which are usually not cancerous (benign), sometimes the gland just increases in size (hyperplasia) and sometimes the reasons are unknown (idiopathic). Only rarely is the cause a cancerous adrenal tumour. Regardless of the cause, increased aldosterone can most commonly lead to low blood levels of potassium (hypokalaemia), increased blood pH (alkalosis), and hypertension. Very rarely, increased aldosterone will lead to high blood levels of sodium (hypernatraemia). Conn's syndrome is the most common cause of secondary hypertension (that is hypertension caused by something other than the working of the heart or blood vessels). Sometimes increased aldosterone will lead to frequent need for urination (polyuria), increased thirst, muscle weakness and cramps, temporary paralysis, headaches, and tingling.

Diagnosing Conn’s syndrome is important because it represents one of the few causes of hypertension that are potentially curable. Although anyone can develop primary hyperaldosteronism, it is most commonly seen 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 usual ways of treating high blood pressure (hypertension). The presence of hypokalaemia in a person with hypertension suggests the need to look for primary hyperaldosteronism and the reason for an increase production of aldosterone. Not all patients have hypokalaemia.

Secondary aldosteronism is when the adrenal glands themselves are not driving the production of aldosterone, when this happens it is not called Conn’s syndrome. It 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, this is called renal artery stenosis. Other causes of secondary hyperaldosteronism include congestive heart failure, cirrhosis, kidney disease, and pre-eclampsia.

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