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PRIMARY HYPERALDOSTERONISM

What is this?
How is the condition diagnosed?
How does the specialist distinguish hyperplasia from an adenoma and why the concern?
What is the treatment?
Are there any side effects with spironolactone?
Will surgery cure the condition?
Can a woman become pregnant with safety in this condition?
How common is primary hyperaldosteronism?

What is this?

In this condition the adrenal gland produces too much aldosterone. Excessive aldosterone makes the kidneys retain sodium (salt) and lose potassium into the urine. Loss of potassium particularly affects muscles causing weakness. The high salt causes the blood pressure to rise, in some cases, to dangerous levels with the risk of heart attack or brain haemorrhage.

How is the condition diagnosed?

1. Blood tests may show a low potassium but in less serious cases blood potassium can be normal.

2. Measuring the ratio of the blood aldosterone to the blood renin. Usually the kidneys release renin when more salt is required. Renin makes its way to the adrenals and causes the release of aldosterone which itself causes the kidneys to hold back salt nad in the process switch off renin production. In primary hyperaldosteronism the adrenals automatically overproduce aldosterone and so renin is suppressed.Therefore measuring the ratio of aldosterone to renin is a handy way of diagnosing the condition. The specialist is suspicious that the patient has the condition if the ratio is greater than 750. 92% of patients with a ratio greater than 750 have primary hyperaldosteronism.

3. As the aldosterone to renin ratio test is not 100% accurate the specialist often will require confirmation.This is often done by determining whether aldosterone is suppressed by giving the patient salt. Normally aldosterone is completely suppressed by additional salt but in primary hyperaldosteronism the aldosterone either does not suppress or does so insufficiently. To do this the patient takes 17 salt capsules per day for three days along with fludrocortisone, a hormone used to hold the additional salt in the body. After three days the blood aldosterone is measured and if still detectable is indicative that the patient has primary hyperaldosteronism. Some centres use instead intravenous salt infusion over 4 hours but this can precipitate heart failure and so is not routinely used.

Once diagnosed the specialist will next determine whether the excess aldosterone is due to;

1. Overactivity of both adrenal glands due in most to the development of tiny nodules. This is called hyperplasia.

2. Overactivity due to a solitary tumour in one adrenal gland. This is known as adenoma or Conn’s tumour

3. There are rare cases due to genetic abnormality (called the chaemeric gene) which causes the adrenals to overproduce aldosterone which unlike the other types is suppressed by giving a glucocorticoid such as dexamethasone.The specialist may diagnose this condition by looking for the chaemeric gene in a blood sample or by giving the patient dexamethasone for at least 5 days and remeasuring blood pressure and aldosterone. In this rare condition aldosterone is suppressed by dexamethasone hence the name given to this rare form namely Dexamethasone Suppressible Hyperaldosteronism. However, if the patient does not have this rare form then dexamethasone can cause the blood pressure to rise with aldosterone levels remaining unaltered so careful monitoring is required.

How does the specialist distinguish hyperplasia from an adenoma and why the concern?

If the patient has hyperplasia then medical therapy with the drug spironolactone will usually suffice. An adenoma requires surgery for it may be curative and also there is a 1% chance of the adenoma being cancerous and so is best removed.

1. In a normal person aldosterone is usually low before arising from bed in the morning. However on getting up and about aldosterone rises and stays up. This is also seen in those with hyperplasia except that the lying and upright levels are usually higher than normally expected. However in an adenoma the aldosterone is often exceptionally high lying but actually decreases on being up and about especially if remeasured at noon when another hormone ACTH is at its lowest level. Hence the specialist measures aldosterone in the early morning before arising and then after the patient has been up and about at noon.

2. CAT scan or MRI scan will often show up an adenoma but sometimes they can be so small and hidden as not to be visible on scanning.

3. Another method is to perform a radioactive adrenal scan. The adrenal tumour takes up more of the radioactivity and so can be easily seen when a special camera takes a radioactive uptake picture of the patients adrenals. In hyperplasia both adrenals are involved and so both take up the radioactivity. This scan is often done while taking dexamethasone to prevent the radioactivity entering the cortisol route rather than the aldosterone production pathway.The amount of radioactivity taken up by the gland equals the amount of hormone being produced and therefore overactive glands show up clearly on the scan.

4. There is another method namely to measure the output of aldosterone from both adrenals by placing a cannula via the groin into the adrenal veins and measuring the hormones. However it is often difficult to reach the right adrenal, the adrenals can be damaged and in 50% of patients the technique is unsuccessful.

What is the treatment?

If due to hyperplasia then treatment is medical with the drug spironolactone. This drug can take a month to work effectively and needs careful monitoring. Curiously often less drug is required with time. If spironolactone is not fully effective then other drugs may be added to control the potassium (e.g amiloride) and blood pressure (e.g.losartan).

Are there any side effects with spironolactone?

If due to adenoma then adrenalectomy is recommended.

Will surgery cure the condition?

Regrettably not all adrenalectomised patients are cured of elevated blood pressure. Why?

Can a woman become pregnant with safety in this condition?

Yes pregnancy is perfectly feasible. Ironically in pregnancy the high blood pressure of hyperaldosteronism settles without spironolactone due to the adosterone effect being blocked by naturally rising progesterone produced by the pregnant patient. This is a major advantage for spironolactone can produce a feminised male fetus. However, within 24hrs of giving birth the progesterone levels fall allowing aldosterone to act once again with a rise in blood pressure to high levels requiring immediate specialist treatment. That is why the patient will be kept in hospital after the pregnancy for observation and spironolactone recommenced on delivery.

How common is primary hyperaldosteronism?

New evidence indicates that 10% of patients with hypertension uncontrolled by more than one antihypertensive drug will have this condition and requires confirmation by measuring the blood ratio of aldosterone to renin.

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NHS Tayside; 2006; version 1.0

Disclaimer; no liability whatsoever is accepted for information given and all such information, especially with regard to drug usage (UK version provided), must be checked with a person’s health provider.