Aldosterone: What Kind of Hormone Is It and What Does the Test Tell You?

Aldosterone is an adrenal hormone that retains sodium, helps excrete potassium, and affects blood pressure. If you have come across this word in a test referral or a report, what follows is a calm breakdown: what exactly is measured and what is discussed with a doctor.

Aldosterone: What Kind of Hormone Is It

Aldosterone is the main mineralocorticosteroid hormone of the adrenal cortex and the only mineralocorticoid that enters the blood. It is produced by the adrenal glands, two small glands above the kidneys. The hormone's action is linked to sodium, potassium, and stable blood pressure.

Key point: aldosterone is an adrenal hormone responsible for salt balance.

Where Aldosterone Is Produced and How It Is Regulated

Synthesis occurs in the zona glomerulosa of the adrenal cortex. It is regulated mainly by angiotensin II, so aldosterone is considered part of the renin-angiotensin-aldosterone system (RAAS). The kidneys produce renin when blood pressure falls: it triggers a chain that prompts the adrenal glands to produce more aldosterone. There is also feedback: potassium concentration acts directly on the zona glomerulosa.

Key point: aldosterone and renin work within the same system.

What Aldosterone Does: Blood Pressure, Potassium, and Sodium

Sodium helps the body retain more water in the bloodstream, and blood pressure rises. Potassium, by contrast, lowers blood pressure: it helps blood vessels relax and helps the kidneys excrete excess sodium. If blood pressure is too low, aldosterone signals the kidneys to return more sodium to the blood and excrete potassium in urine, and blood pressure rises. When it returns to normal, the hormone level decreases. Under its action, circulating blood volume increases.

Key point: the hormone retains sodium and water and excretes potassium.

Aldosterone Test: When It Is Ordered

The test measures the amount of aldosterone in blood or urine. It is most often done together with a renin test, which gives the aldosterone-renin ratio. It is discussed in cases of high blood pressure with low potassium, blood pressure that does not improve on standard medications or appeared at a young age, sodium and potassium abnormalities, and a sharp drop in blood pressure with dizziness on standing. The hormone level depends on body position, so before the test you may be asked to lie down or stand. For a urine test, all urine is collected over 24 hours in a special container. Before the test, the doctor will explain whether special preparation is needed, including regarding medications and diet.

Key point: aldosterone is assessed together with renin, with preparation according to the doctor's instructions.

What High and Low Aldosterone Mean

The number is interpreted together with other tests. An increase occurs in primary and secondary hyperaldosteronism. Primary is linked to a problem in the adrenal glands themselves, most often a benign tumor producing excess hormone. Secondary is caused by a factor outside the adrenal glands: genes, diet, heart, liver, or kidney disease, or high blood pressure. Manifestations of excess: high blood pressure, low potassium and/or high sodium, muscle weakness, cramps, fatigue, headache, heart rhythm disturbances, thirst, and frequent urination. This occurs mainly at ages 30–50 and often becomes a cause of midlife hypertension. A decrease (hypoaldosteronism) occurs in adrenal insufficiency, Addison's disease: the glands are damaged and produce less hormone, more often due to an immune disorder, sometimes due to infections or tumor cells. Manifestations: low blood pressure, high potassium and/or low sodium, fatigue, weakness, loss of appetite, weight loss, abdominal pain.

To determine the cause, the doctor may order:

• blood tests for aldosterone and renin;
• blood potassium and urine aldosterone;
• ECG, kidney ultrasound, abdominal CT;
• in some cases, adrenal vein catheterization.

Key point: the aldosterone number is compared with renin, potassium, and sodium.

When to See a Doctor

A reason to see a doctor is symptoms of excess aldosterone, especially if blood pressure is difficult to control, rose at a young age, or is combined with low potassium. A planned discussion is also needed for persistent fatigue, muscle weakness, cramps, headache, and thirst.

An aldosterone abnormality alone is not a reason to call an ambulance. 103 or 112 is for life-threatening signs, for example suspected stroke or heart attack.

Key point: a discussion with a doctor is needed not because of a single number but based on the combination of symptoms and tests. This material is for reference and does not replace a doctor's consultation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer