Primary hyperaldosteronism (Conn syndrome) !
The adrenal glands make too much aldosterone, causing high blood pressure and sometimes low potassium. A curable cause of hypertension.
Updated 2026-11-01
Structures involved
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Why it happens
- Aldosterone: actions and control
- The renin–angiotensin–aldosterone system
- Distal tubule and collecting duct
- Potassium balance
- Metabolic alkalosis and its compensation
- Adrenal cortex zones and medulla
What it is
Autonomous overproduction of aldosterone by one or both adrenal glands, independent of renin. It is the most common curable form of secondary hypertension.
Who gets it
Present in a notable share of people with hypertension and more in resistant hypertension, yet greatly underdiagnosed because screening is rarely done. Low potassium is seen in only a minority.
Causes
- Bilateral adrenal hyperplasia (idiopathic hyperaldosteronism)
- Aldosterone-producing adenoma (Conn syndrome)
- Rare: unilateral hyperplasia, adrenal carcinoma, familial forms (glucocorticoid-remediable aldosteronism)
Risk factors
- Resistant or severe hypertension
- Hypertension with spontaneous or diuretic-induced hypokalaemia
- Hypertension with an adrenal incidentaloma
- Hypertension with sleep apnoea or atrial fibrillation
- Family history of early hypertension or stroke
Pathophysiology
Excess aldosterone acts on the distal nephron, increasing sodium reabsorption and potassium and hydrogen excretion. Volume expansion raises blood pressure and suppresses renin. Partial escape from sodium retention explains why oedema is uncommon. Aldosterone also has direct pro-fibrotic effects on the heart, vessels and kidney.
Classification
- Unilateral disease (adenoma or unilateral hyperplasia): potentially surgically curable
- Bilateral disease (bilateral hyperplasia): treated medically
Symptoms and signs
- Often none apart from hypertension
- Muscle weakness, cramps and fatigue from hypokalaemia
- Polyuria and nocturia
- Palpitations
- Headache
Diagnosis
- Clinical
- Screen hypertensive patients in high-risk groups, such as resistant hypertension, hypokalaemia, adrenal incidentaloma or young onset.
- Tests
- Screening with the aldosterone-to-renin ratio (high aldosterone, suppressed renin), after correcting potassium. Confirmation with a saline infusion, oral salt loading or captopril challenge test. Adrenal vein sampling to tell unilateral from bilateral disease before surgery.
- Imaging
- Adrenal CT to exclude carcinoma and look for an adenoma; CT alone does not reliably show which side is secreting.
Differential diagnosis
- Essential hypertension
- Secondary hyperaldosteronism (renal artery stenosis, diuretics, heart failure, cirrhosis), with high renin
- Cushing syndrome
- Liddle syndrome or apparent mineralocorticoid excess (liquorice), with low aldosterone
Goal of treatment
Normalise blood pressure and potassium, and remove or block the effects of aldosterone to protect the heart, kidney and brain.
Treatment
- Surgical
- Laparoscopic adrenalectomy for unilateral disease confirmed by adrenal vein sampling; it cures or improves hypertension and normalises potassium.
- Medical
- Mineralocorticoid receptor antagonists (spironolactone, eplerenone) for bilateral disease or when surgery is not possible; amiloride as an alternative; other antihypertensives as needed.
- Follow-up
- Blood pressure, potassium and kidney function, especially when starting antagonists (risk of hyperkalaemia) and after surgery.
- Lifestyle
- Low-sodium diet, which reduces potassium loss and helps blood pressure.
Complications
- Higher risk of stroke, myocardial infarction, atrial fibrillation and heart failure than in essential hypertension with the same blood pressure
- Left ventricular hypertrophy
- Chronic kidney disease
- Arrhythmias from hypokalaemia
Prognosis
Unilateral disease can be cured or much improved by surgery; bilateral disease is controlled with medication. Early diagnosis limits cardiovascular and kidney damage.
Test yourself
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What is the best screening test for primary hyperaldosteronism?
The plasma aldosterone-to-renin ratio: high aldosterone with suppressed renin.
What metabolic pattern is classic for hyperaldosteronism?
Hypertension, hypokalaemia and metabolic alkalosis, with low renin.
Why is adrenal vein sampling done before surgery?
To confirm the secreting side, because CT cannot reliably tell a functioning adenoma from bilateral disease or an incidental nodule.
Which drug class treats bilateral adrenal hyperplasia?
Mineralocorticoid receptor antagonists such as spironolactone or eplerenone.
Related conditions
- Arterial hypertension
- Cushing syndrome
- Phaeochromocytoma
- Atrial fibrillation
- Chronic kidney disease
- Hypertensive heart disease
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Primary and secondary hyperaldosteronism (MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine), 2025).
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