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Aldosterone is a hormone – the main mineralocorticosteroid produced by the glomerular layer of the adrenal cortex. Influences the regulation of the plasma concentration of electrolytes: sodium and potassium. We perform aldosterone testing, among others, in the diagnosis of hypokalemia or disorders of the water and electrolyte balance.
Aldosterone – characteristics
Aldosterone is a steroid hormone produced by the glomerular layer of the adrenal cortex. Its secretion is influenced by many factors, including an increase in the level of potassium ions or a decrease in blood pressure. Aldosterone regulates the plasma concentration of the most important electrolytes: sodium and potassium. It inhibits the excretion of sodium ions by the kidneys at the expense of increased removal of potassium ions. The correct level of potassium and sodium has a positive effect on the body’s hydration and proper blood pressure. The main stimulus increasing the synthesis of aldosterone is the stimulation of the renin-angiotensin system and the activation of the sympathetic nervous system. The kidney begins to produce potassium in response to low blood pressure or the level of potassium renaissance, i.e. the enzyme catalyzing the reaction of which it is angiotensyna. Under its influence, the adrenal glands begin to release aldosterone.
When do we do the aldosterone test?
Both excessive secretion and insufficient secretion of aldosterone are detrimental to humans. For this reason We perform aldosterone testing in the following situations:
1. The risk of secondary hypertension (when the cause of hypertension is the presence of an aldosterone producing tumor).
2. Diagnosis of hypokalemia (low potassium levels).
3. Disorders of the water and electrolyte balance (edema).
4. Chronic heart, liver and kidney failure.
5. Presence of symptoms suggestive of hyperaldosteronism (increased thirst, severe hypertension, increased urine output).
6. Presence of symptoms of low potassium levels (numbness, weakness, muscle spasms and abnormal heart rhythms).
7. Suspected hypoaldosteronism (insufficient aldosterone excretion) characterized by low blood pressure and weakness.
8. Symptoms of high levels of potassium in the body (weakness and abnormal heart rhythm).
What are the contraindications for the study?
A small amount of material is enough to perform the test, therefore there are no contraindications.
Preparation for aldosterone testing
The amount of aldosterone secreted depends, among other things, on stress, diet, medications, exercise and body position. For this reason, before performing the aldosterone test, you should consult your doctor to determine how to modify your diet and what medications to stop taking during the test so that the result is more accurate. The position of the body during blood collection is also important. Sometimes doctors recommend that you stand up for 15 minutes before the blood sample is drawn. Sometimes blood is collected in the supine position, when the patient has not yet managed to get out of bed.
Aldosterone Test Material: serum or daily urine collection (the choice of method depends on the doctor).
Preparation for aldosterone testing: the test is performed under the conditions of the usual diet of sodium (table salt, 100-120 mmol / day) and potassium (40-70 mmol / day), after correcting any electrolyte disturbances, after night rest, on an empty stomach (at least 8 hours) and XNUMX/XNUMX urine collection.
The course of the study: one-time blood sampling from a vein in the arm (it is a clearly visible vein and easy to puncture). The puncture is made with a thin needle and blood is drawn into the syringe. The material collected in this way is sent for further analysis. As for the daily urine collection – it should be started in the morning of a sleepless night. The first urine should be sent to the toilet, and each subsequent urine should be transferred to a special container (remember to wash your intimate area before urinating). The last portion of urine should be placed in the container the next night after the collection begins.
Waiting time for aldosterone result: 1 Day.
Standard: 140–560 pmol/l (5–20 ng/dl).
Comments: Saving sodium ions causes water retention in the body and hypervolaemia; as a result, blood pressure rises. Many authors list hyperaldosteronism as the most common cause of secondary arterial hypertension.
What causes high aldosterone levels?
Do secondary aldosteronism it occurs as a result of the presence of other ailments, e.g .:
- narrowing of the kidney artery (it is narrowed by the blood supply to the kidney and is impaired),
- dehydration,
- nephrotic syndrome,
- low sodium content in the diet,
- pregnancy,
- Bartter’s syndrome,
- cirrhosis of the liver (when the liver is unable to produce enough albumin),
- a tumor that produces renin,
- heart failure (the heart cannot ensure proper blood flow through the kidneys, which is a sign of dehydration).
Primary aldosteronism (Conn’s syndrome) is much less common. Its most common cause is the presence of adrenal adenocarcinoma or an overgrowth of the glomerular layer of the adrenal cortex.
The causes of low aldosterone levels
The reasons for the decreased level of aldosterone are believed to be:
- Addison’s disease (primary adrenal insufficiency) – resulting from tuberculosis or other infections,
- kidney dysfunction which is a complication of long-term diabetes,
- hypokalemia,
- taking a certain class of drugs, e.g. angiotensin II receptor antagonists, angiotensin converting enzyme (ACE-I) inhibitors, NSAIDs (non-steroidal anti-inflammatory drugs) and beta-blockers.
Norms of aldosterone test results
The correct result is influenced by many additional factors, one should take into account, for example, the patient’s condition, age or sex. The obtained results should be immediately consulted with a doctor who will decide on the further procedure.
- Plasma aldosterone norm: 140-560 pmol / L (5-20 ng / dL).
- Aldosterone norm from the daily urine dose: within 14-53 nmol / 24h (5-19µg / 24h).