Aldosterone and Renin

Aldosterone is a hormone which controls sodium retention and expulsion of potassium in the kidneys; it is responsible for maintaining normal levels of sodium and potassium in the bloodstream and also helps to regulate blood pressure. Aldosterone is produced by the adrenal glands, which are situated at the top of the kidneys; the production of aldosterone is controlled by renin and angiotensin. Renin is a chemical which is released from the kidneys when there is a decrease in sodium levels or blood pressure or an increase in the concentration of potassium.

Why is the test used?

The test is used to assess levels of renin and aldosterone in the blood. The test is usually recommended for patients who show symptoms of an increased production of aldosterone; these include high blood pressure, low levels of potassium and weakness in the muscles.

How is the test performed?

The test is done by collecting a sample of blood from a vein in the arm; however, some doctors may also request a sample from the adrenal or renal veins (this has to be done in a hospital setting using a catheter). Some doctors prefer to use a 24 hour urine test because the results of a blood test can be affected by the time of the day and the position of the patient. To increase the accuracy of the blood test, the doctor may ask the patient to either stay upright or lie down for a period of time before the test is performed.

What do the results mean?

The levels of aldosterone, renin and cortisol may indicate a number of different health conditions, including:

  • Primary hyperaldosteronism (also known as Conn’s syndrome): high aldosterone, normal cortisol, low renin
  • Secondary hyperaldosteronism: high aldosterone, normal cortisol, high renin
  • Addison’s disease (also known as adrenal insufficiency): low aldosterone, low cortisol, high renin
  • Cushing’s syndrome: low-normal aldosterone, high cortisol, low renin

Hyperaldosteronism is a condition, which occurs when too much aldosterone is produced; primary hyperaldosteronism is usually caused by a benign tumour on the adrenal gland, while secondary hyperaldosteronism, which is much more common, is usually caused by health problems which decrease sodium levels, decrease blood pressure and decrease blood flow to the kidneys.

Certain medications, including beta blockers, steroids, diuretics and oral contraceptives, may influence the results of the test.

Specific Blood Tests

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