Aldosterone - 24 hrs urine

Aldosterone – 24 Hours Urine is a laboratory test that measures the total amount of aldosterone excreted in urine over a complete 24-hour period. Aldosterone is a steroid hormone produced by the outer layer of the adrenal glands, which are located above the kidneys.

Aldosterone helps control blood pressure and maintains the balance of sodium, potassium, and water in the body. A 24-hour urine collection captures hormone excretion throughout the day and may reduce the effect of short-term fluctuations that can influence a single blood measurement.

Benefits of the Test

• Measures total aldosterone excretion over 24 hours.
• Supports evaluation of excessive aldosterone production.
• Helps investigate resistant or difficult-to-control hypertension.
• Supports assessment of unexplained low potassium levels.
• May help evaluate suspected primary aldosteronism.
• Provides information about adrenal-gland hormone function.
• May be used during confirmatory evaluation after abnormal screening results.
• Reduces the influence of short-term hormone fluctuations.
• Can be interpreted with urine sodium, renin, and blood aldosterone results.
• Supports treatment planning under specialist guidance.

Why Doctors Recommend This Test

Doctors may recommend this test when a patient has persistent high blood pressure, hypertension requiring several medicines, unexplained low potassium, muscle weakness, excessive thirst, frequent urination, or an adrenal abnormality identified through imaging.

It may also be used after an abnormal aldosterone-to-renin ratio or as part of a confirmatory salt-loading assessment. The testing conditions and preparation requirements may differ depending on why the test has been ordered.

Preparation Before Test

• Follow the doctor’s instructions regarding salt intake before and during collection.
• Do not change to a high-salt or low-salt diet unless specifically advised.
• Inform the doctor about all blood-pressure medicines, diuretics, steroids, and supplements.
• Do not stop or change prescribed medicines without medical supervision.
• Inform the doctor about potassium supplements or liquorice-containing products.
• Use the collection container and preservative provided by the laboratory.
• Record the exact starting and ending times of the collection.
• Collect every urine sample passed during the specified 24-hour period.
• Store the container exactly as instructed during collection.
• Inform the laboratory if any urine was missed, spilled, or collected outside the scheduled period.

Normal Reporting Time

The Aldosterone – 24 Hours Urine test requires completion of the 24-hour collection followed by specialised biochemical analysis, validation, and quality review. Results are generally available within a few working days after the completed sample is submitted. Exact reporting time may vary according to the testing schedule and laboratory workflow.

Who Should Take This Test?

This test may be recommended for:

• Patients with resistant or difficult-to-control hypertension.
• Individuals with high blood pressure at a young age.
• Patients with hypertension and unexplained low potassium.
• Individuals with an abnormal aldosterone-to-renin ratio.
• Patients with a suspected aldosterone-producing adrenal adenoma.
• Individuals with adrenal enlargement or an adrenal incidentaloma.
• Patients being evaluated for primary aldosteronism.
• Individuals undergoing a specialist-directed salt-loading assessment.
• Patients receiving follow-up for a diagnosed aldosterone disorder.
• People specifically advised to undergo 24-hour urinary aldosterone testing by an endocrinologist.

Detailed Information

Aldosterone is produced in the zona glomerulosa of the adrenal cortex. Its secretion is primarily controlled by the renin-angiotensin system and the potassium concentration in the blood. ACTH, sodium intake, hydration, posture, and certain medicines can also influence aldosterone production.

When blood flow to the kidneys decreases, the kidneys release renin. This initiates a sequence that produces angiotensin II, which stimulates the adrenal glands to release aldosterone. Aldosterone then signals the kidneys to retain sodium and water while increasing potassium excretion.

Excess aldosterone may cause sodium retention, increased blood volume, high blood pressure, and low potassium. Primary aldosteronism occurs when the adrenal glands produce aldosterone independently of normal regulatory signals.

Possible causes of primary aldosteronism include an aldosterone-producing adrenal adenoma, bilateral adrenal hyperplasia, and less commonly inherited or other adrenal conditions. Many affected patients do not have obvious low potassium, so normal potassium does not exclude the disorder.

Secondary hyperaldosteronism occurs when increased renin activity stimulates aldosterone production. It may be associated with reduced blood flow to the kidneys, renal artery narrowing, heart failure, liver disease, or other conditions that reduce effective circulating blood volume.

Low aldosterone may occur with adrenal insufficiency, certain kidney disorders, reduced renin production, severe illness, or medicines that interfere with the renin-angiotensin-aldosterone system. The clinical meaning depends on renin, cortisol, electrolytes, blood pressure, and other findings.

Aldosterone secretion changes throughout the day and is affected by posture and activity. A 24-hour urine sample represents cumulative excretion and can provide a broader assessment than a single blood sample under selected circumstances.

For certain confirmatory protocols, the doctor may prescribe a specific sodium intake before collection and request 24-hour urine sodium along with aldosterone. Urinary sodium helps determine whether sodium intake was adequate for the intended interpretation.

Accurate collection is essential. On the starting morning, the patient usually empties the bladder and does not add that first urine to the container. The starting time is recorded. Every subsequent urine sample is collected, including the first urine passed at the same time the next morning.

If any urine is missed, the measured 24-hour aldosterone may be falsely low. Excess collection time, incorrect storage, failure to use the required preservative, or contamination can also reduce result reliability.

Many medicines influence aldosterone or renin. These include diuretics, beta-blockers, ACE inhibitors, angiotensin-receptor blockers, mineralocorticoid-receptor antagonists, and certain calcium-channel blockers. Medication adjustment must only occur under medical supervision because stopping blood-pressure treatment may be unsafe.

The test cannot independently identify whether excess aldosterone comes from one adrenal gland or both. Additional evaluation may include blood aldosterone and renin, electrolyte testing, confirmatory suppression tests, adrenal CT, and adrenal-vein sampling.

Reference ranges depend on sodium intake, collection protocol, analytical method, and laboratory standards. Results should always be interpreted using the reference information printed on the individual report.

At Focus Diagnostics, 24-hour urinary aldosterone testing is performed using established biochemical methods, appropriate specimen-handling procedures, and laboratory quality controls to provide reliable results for endocrine interpretation.