Primary aldosteronism
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What Is Primary Aldosteronism?
Primary aldosteronism is a disease caused by an excess production of the normal adrenal hormone aldosterone. This hormone is responsible for sodium and potassium balance, which then directly controls water balance to maintain appropriate blood pressure and blood volume.
Primary aldosteronism is a disease caused by an excess production of the normal adrenal hormone aldosterone. This hormone is responsible for sodium and potassium balance, which then directly controls water balance to maintain appropriate blood pressure and blood volume.
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What Causes Primary Aldosteronism?
People with a deficiency of aldosterone, especially found in association with cortisol deficiency in Addison’s disease, have low blood volume and therefore low blood pressure, low sodium, and high potassium. Just the opposite is seen in aldosteronism. Primary aldosteronism causes high blood pressure and a low serum potassium. The serum sodium is usually in the normal range. A separate disorder called secondary aldosteronism is the result of abnormal fluid shifts seen in congestive heart failure, liver disease and certain kidney diseases. Primary aldosteronism used to be considered a rare disease, but recent studies show it to be a fairly common cause of hypertension. It is usually considered by physicians if they find an unexpectedly low potassium in a person being treated for hypertension. However, many people with this disease have potassium levels in the normal range. There is a growing awareness that many people with difficult to control hypertension or progressively worsening hypertension may have primary aldosteronism. While most individuals have no specific symptoms, some may have fatigue, headaches, muscle weakness, numbness or cramps, and excessive urination, especially at night. The physical examination is usually normal except for the elevated blood pressure. The prevalence of PA is uncertain, but is probably about 5% of all hypertensives and as high as 20% of treatment resistant hypertensives. There are two major types of primary aldosteronism and three rare forms.
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How is Primary Aldosteronism Diagnosed?
When primary aldosteronism is considered by a physician, tests are done to look for an excess of the hormone aldosterone in the blood and urine, and also a suppressed plasma renin. The initial screening test is the aldosterone/renin ratio. To be certain that the value is accurate, serum potassium must be corrected first, and blood pressure medications that can affect aldosterone or renin must be discontinued for a few weeks. Borderline test results are common, so repetition of the ratio is often needed.
Other tests, looking at other adrenal steroid hormones, can be very useful as well as tests looking for the normal physiologic changes in hormones in the morning and evening, as well as responses to sodium challenge or sodium restriction.
Once primary aldosteronism is confirmed, it is important to try to differentiate a single adenoma from hyperplasia. A CT of the adrenals will often show a small tumor in one of the adrenals. Typically, the adrenal tumors that cause aldosteronism are very small, usually less than 2 cm. The presence of a tumor on CT is not adequate proof of an adenoma as the cause of the disease. Often it is misleading, with a tiny adenoma on the other side and a non-functioning tumor that is seen on the CT.
The gold standard for confirming unilateral disease is the use of adrenal vein sampling. This is a special procedure performed in major medical centers with experienced radiologists. Catheters are inserted in both adrenal veins and blood samples are obtained before and after ACTH infusion looking for a significant difference in levels of aldosterone between the two sides. If there is a significant difference, an adenoma is confirmed. Unfortunately, this procedure is not always diagnostic because it is difficult to get a catheter in the right adrenal vein.
When primary aldosteronism is considered by a physician, tests are done to look for an excess of the hormone aldosterone in the blood and urine, and also a suppressed plasma renin. The initial screening test is the aldosterone/renin ratio. To be certain that the value is accurate, serum potassium must be corrected first, and blood pressure medications that can affect aldosterone or renin must be discontinued for a few weeks. Borderline test results are common, so repetition of the ratio is often needed.
Other tests, looking at other adrenal steroid hormones, can be very useful as well as tests looking for the normal physiologic changes in hormones in the morning and evening, as well as responses to sodium challenge or sodium restriction.
Once primary aldosteronism is confirmed, it is important to try to differentiate a single adenoma from hyperplasia. A CT of the adrenals will often show a small tumor in one of the adrenals. Typically, the adrenal tumors that cause aldosteronism are very small, usually less than 2 cm. The presence of a tumor on CT is not adequate proof of an adenoma as the cause of the disease. Often it is misleading, with a tiny adenoma on the other side and a non-functioning tumor that is seen on the CT.
The gold standard for confirming unilateral disease is the use of adrenal vein sampling. This is a special procedure performed in major medical centers with experienced radiologists. Catheters are inserted in both adrenal veins and blood samples are obtained before and after ACTH infusion looking for a significant difference in levels of aldosterone between the two sides. If there is a significant difference, an adenoma is confirmed. Unfortunately, this procedure is not always diagnostic because it is difficult to get a catheter in the right adrenal vein.
How Is Primary Aldosteronism Treated?
The treatment of primary aldosteronism depends on the cause. If there is a single tumor, surgical removal of that tumor can cure the disease. The remaining adrenal gland is usually normal and individuals with this form of the disease will have enough adrenal hormone production from the remaining gland to live normally. Unfortunately, quite often there is still some residual hypertension even after the surgery, so sometimes antihypertensive medication is still necessary.
If bilateral hyperplasia is the cause of aldosteronism, or if surgery for an adenoma is not appropriate or safe, the disorder is treated with specific medications that block the effect of aldosterone. There are three such medications: spironolactone (Aldactone), eplerenone (Inspra) and amiloride (Midamor). These medications are very effective, but it is common to need to combine them with other antihypertensive medications for the management of hypertension in individuals with aldosteronism.
The treatment of primary aldosteronism depends on the cause. If there is a single tumor, surgical removal of that tumor can cure the disease. The remaining adrenal gland is usually normal and individuals with this form of the disease will have enough adrenal hormone production from the remaining gland to live normally. Unfortunately, quite often there is still some residual hypertension even after the surgery, so sometimes antihypertensive medication is still necessary.
If bilateral hyperplasia is the cause of aldosteronism, or if surgery for an adenoma is not appropriate or safe, the disorder is treated with specific medications that block the effect of aldosterone. There are three such medications: spironolactone (Aldactone), eplerenone (Inspra) and amiloride (Midamor). These medications are very effective, but it is common to need to combine them with other antihypertensive medications for the management of hypertension in individuals with aldosteronism.
