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Aldosterone
(Mineralocorticoid Hormone – Adrenal Cortex)
Synonyms
- Aldosterone
- ALD
- Mineralocorticoid hormone
- 18-Aldosterone
- C21 steroid hormone
- Adrenal cortex – Zona glomerulosa hormone
Units of Measurement
nmol/L, ng/mL, ng/dL, ng/100mL, ng%, ng/L, pg/mL
Description
Aldosterone is the primary mineralocorticoid hormone produced by the zona glomerulosa of the adrenal cortex.
It is part of the Renin–Angiotensin–Aldosterone System (RAAS) and plays a key role in:
- Sodium retention
- Potassium excretion
- Water balance
- Blood pressure regulation
Aldosterone secretion is stimulated by:
- Angiotensin II (strongest)
- Hyperkalemia
- ACTH (mild/short-term)
Measurement is essential for diagnosing:
- Primary aldosteronism (Conn syndrome)
- Secondary hyperaldosteronism
- Adrenal insufficiency
- Hypertension workup
Physiological Role
1) Sodium & Water Regulation
Aldosterone acts on kidney distal tubules and collecting ducts to:
- Increase Na+ reabsorption
- Increase water retention
- Increase K+ excretion
- Increase H+ excretion
2) RAAS System
Triggered by:
- Low blood pressure
- Low renal perfusion
- Low sodium
- High potassium
3) Cardiovascular Effects
Chronic high aldosterone causes:
- Hypertension
- Left ventricular hypertrophy
- Endothelial dysfunction
Clinical Significance
Elevated Aldosterone
1. Primary Aldosteronism (PA)
Most important cause of secondary hypertension.
Causes:
- Aldosterone-producing adenoma (APA)
- Bilateral adrenal hyperplasia (BAH)
- Familial hyperaldosteronism
Key biochemical pattern:
- High aldosterone
- Low renin
- High aldosterone/renin ratio (ARR)
2. Secondary Hyperaldosteronism
Due to excess RAAS activation:
- Renal artery stenosis
- Renin-secreting tumors
- Congestive heart failure
- Cirrhosis
- Nephrotic syndrome
- Pregnancy
3. Other Causes
- Potassium depletion
- Diuretics
- Oral contraceptives
- Malignant hypertension
Low Aldosterone
Occurs in:
- Addison disease (primary adrenal insufficiency)
- Hyporeninemic hypoaldosteronism
- Diabetic kidney disease
- ACE inhibitors / ARBs
- Heparin therapy (direct suppression)
- Genetic defects (aldosterone synthase deficiency)
Reference Intervals
Values depend heavily on posture, sodium intake, and time of day.
Adults – Morning (Sitting / Upright)
- 4 – 31 ng/dL
- 0.11 – 0.86 nmol/L
Supine
- < 16 ng/dL
- < 0.44 nmol/L
Children
- Generally higher than adults due to RAAS activity
- 7 – 99 ng/dL (age-dependent)
Plasma Aldosterone–Renin Ratio (ARR)
- High ARR = suggests Primary Aldosteronism
(Exact cutoff depends on renin method)
Interpretation MUST always be done with simultaneous renin measurement.
Sample Collection Requirements
Aldosterone is posture-sensitive.
For reliable interpretation:
- Morning sample
- Maintain posture for ≥2 hours upright, if evaluating ARR
- Low-sodium diet ↑ aldosterone
- High-sodium diet ↓ aldosterone
- Avoid hemolysis and prolonged storage
Drugs that affect aldosterone
Should be withdrawn (if clinically safe):
⬆ Increases aldosterone:
- Beta blockers
- NSAIDs
- Oral contraceptives
- Decongestants
⬇ Decreases aldosterone:
- ACE inhibitors / ARBs
- Diuretics
- Spironolactone / eplerenone
- Heparin
Unit Meanings
| Unit | Meaning |
| nmol/L | nanomole per liter |
| ng/mL | nanogram per milliliter |
| ng/dL | nanogram per deciliter |
| ng/100mL | equal to ng% |
| ng% | nanogram per 100 mL |
| ng/L | nanogram per liter |
| pg/mL | picogram per milliliter |
Analytical Notes
- LC-MS/MS is the gold standard for aldosterone measurement.
- Immunoassays may show cross-reactivity → falsely high results.
- Posture, sodium intake, and medications dramatically alter results.
- Always interpret with simultaneous plasma renin.
Clinical Pearls
- Aldosterone is one of the most posture-sensitive hormones.
- High aldosterone + suppressed renin = strongly suggestive of Primary Aldosteronism.
- Early-morning upright sampling improves diagnostic accuracy.
- Spironolactone must be stopped 4–6 weeks before ARR testing.
- In Addison disease, aldosterone is low despite high renin.
Interesting Fact
Aldosterone was discovered in 1953 (England), earning the discoverers Nobel Prize nominations for defining RAAS physiology - foundational to modern hypertension management.
References
- Tietz Clinical Chemistry and Molecular Diagnostics, 8th Edition - Adrenal Hormone Section.
- ESAP 2024 - Aldosterone & Renin Reference Intervals.
- Endocrine Society Clinical Practice Guidelines - Primary Aldosteronism.
- Mayo Clinic Laboratories - Aldosterone, Plasma Test.
- ARUP Consult - Aldosterone & Renin Interpretation.
- NIH / NIDDK - Aldosterone and RAAS Physiology.
- Funder JW et al. J Clin Endocrinol Metab - PA diagnostic criteria.