Hyperaldosteronism (Conn's syndrome)

It is a condition in which too much of the blood pressure hormone, aldosterone, is made by one or both adrenal glands. When aldosterone is over-produced, too much salt remains in the body and this results in a rise in blood pressure. Around half of the patients diagnosed with primary hyperaldosteronism (PH) will be found to have low potassium levels in their blood. PH affects at least 5 per cent, if not slightly more, of people who have high blood pressure.

People with PH are usually referred to hospital with high blood pressure (hypertension) which has proved difficult to control, despite a number of medications. If they are among the 50% of PH patients who have reduced potassium in their blood, they may also be affected by tiredness, increased urination and thirst. 

PH is diagnosed with a blood test which calculates the ratio of the hormones aldosterone and renin in the bloodstream. If the aldosterone level is high and the renin low or undetectable, PH is suspected and the test is repeated to confirm the diagnosis. The next step in the diagnostic process is to image the adrenal glands, located on top of the kidneys, via a CT or MRI scan. This can help in identifying the presence of the fatty nodule which is overproducing the aldosterone. However, this is often too small to visualise.

A definitive diagnosis of PH can be made by means of adrenal vein sampling. This is a day procedure undertaken by a consultant radiologist. A catheter is fed into the femoral vein in the groin and blood samples are taken from the adrenal veins. This test will establish whether only one or both adrenal glands are causing the condition.

If only one adrenal gland is causing the PH, it can be removed with a keyhole procedure called laparoscopic adrenalectomy. This should either improve the control of the high blood pressure or, in some cases, completely cure it. If low potassium is also a feature, this is usually corrected too.

If both adrenal glands are responsible for the condition,  or if the patient is found to have a genetic cause for PH (and this will have been tested for before adrenal vein sampling was undertaken) treatment with an anti-aldosterone hormone tablet such as Spironolactone, will be commenced.  This long-term treatment is effective in reducing blood pressure and correcting low potassium, if present.

Patients will also be advised to maintain a low-salt diet. If potassium needs to be supplemented, this can be by diet or medication. Initial review following operative or medical treatment is in clinic and any further follow-up can continue there or transfer to the GP’s surgery. The prognosis following treatment for PH is excellent.

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