Conn’s Syndrome (Primary Hyperaldosteronism)

High blood pressure is one of the most common health problems worldwide. While most cases are classified as essential hypertension, meaning there is no identifiable cause, a significant number of people have high blood pressure because of an underlying medical condition. One such condition is Conn’s syndrome, a hormonal disorder that is often underdiagnosed but highly treatable.

Conn’s syndrome occurs when the adrenal glands produce too much aldosterone, a hormone responsible for regulating sodium, potassium, and blood pressure. Excess aldosterone causes the body to retain sodium and water while losing potassium, leading to persistent hypertension and various other health issues.

The good news is that early diagnosis and appropriate treatment can significantly improve blood pressure control and reduce the risk of heart disease, stroke, kidney damage, and other complications.

In this comprehensive guide, you’ll learn everything about Conn’s syndrome, including its causes, symptoms, diagnostic tests, treatment options, and answers to the most frequently asked questions.

What Is Conn’s Syndrome?

Conn’s syndrome, also known as primary hyperaldosteronism, is a condition in which one or both adrenal glands produce excessive amounts of aldosterone independent of the body’s normal regulatory mechanisms.

The adrenal glands are two small glands located above the kidneys. They produce several important hormones, including:

• Aldosterone
• Cortisol
• Adrenaline
• Noradrenaline

Among these, aldosterone plays a crucial role in maintaining:

• Blood pressure
• Fluid balance
• Sodium levels
• Potassium levels

When aldosterone is produced in excess, the body retains too much sodium and water while losing potassium through the urine. This leads to high blood pressure, low potassium levels, muscle weakness, and an increased risk of cardiovascular disease.

What Is Another Name for Conn’s Syndrome?

Another name for Conn’s syndrome is Primary Hyperaldosteronism.

The condition was first described in 1955 by American endocrinologist Dr. Jerome Conn, after whom it is named.

Today, healthcare professionals often use the terms Conn’s syndrome and primary hyperaldosteronism interchangeably. Technically, however, Conn’s syndrome originally referred specifically to aldosterone excess caused by an adrenal adenoma, whereas primary hyperaldosteronism also includes other causes such as bilateral adrenal hyperplasia.

How Common Is Conn’s Syndrome?

Researchers now believe Conn’s syndrome is much more common than previously thought.

Studies estimate that it affects:

• Around 5–10% of people with high blood pressure
• Up to 20% of patients with resistant hypertension
• Many individuals with unexplained low potassium levels

Because symptoms may be subtle, many people remain undiagnosed for years.

What Causes Conn’s Syndrome?

Conn’s syndrome develops when the adrenal glands produce excessive aldosterone.

The most common causes include:

1. Adrenal Adenoma (Conn’s Adenoma)

This is a benign (non-cancerous) tumour of one adrenal gland.

It is responsible for approximately 30–40% of cases.

2. Bilateral Adrenal Hyperplasia

Both adrenal glands become enlarged and produce excessive aldosterone.

This accounts for approximately 60% of cases.

3. Familial Hyperaldosteronism

Certain inherited genetic mutations cause excess aldosterone production.

Although uncommon, it tends to run in families.

4. Adrenal Carcinoma

Rarely, a malignant adrenal tumour may produce aldosterone.

Risk Factors

Certain people are more likely to develop Conn’s syndrome, including those with:

• Resistant hypertension
• Hypertension before age 40
• Family history of early hypertension
• Low potassium levels
• Adrenal nodules discovered incidentally
• Family history of strokes at a young age

How Does Aldosterone Work?

Aldosterone acts primarily on the kidneys.

It tells the kidneys to:

• Reabsorb sodium
• Retain water
• Excrete potassium
• Excrete hydrogen ions

This increases blood volume and raises blood pressure.

When too much aldosterone is produced, blood pressure remains persistently elevated, regardless of the body’s actual needs.

What Organ Regulates Aldosterone?

Aldosterone is produced by the adrenal cortex, specifically the zona glomerulosa of the adrenal glands.

Its production is mainly regulated by the renin-angiotensin-aldosterone system (RAAS), in which the kidneys play a central role by releasing renin in response to low blood pressure or reduced blood flow. Potassium levels in the blood also directly influence aldosterone secretion.

In Conn’s syndrome, however, aldosterone production becomes largely independent of the normal RAAS control, leading to persistently high aldosterone levels and suppressed renin.

What Is the Main Target Organ of Aldosterone?

The primary target organ of aldosterone is the kidney, particularly the distal tubules and collecting ducts.

However, excessive aldosterone also affects:

• Blood vessels
• Heart muscle
• Brain
• Kidneys themselves

This explains why untreated Conn’s syndrome increases cardiovascular risk beyond its effect on blood pressure alone.

Early Signs of High Aldosterone

Many people have no symptoms initially.

Early signs include:

• Persistent high blood pressure
• Difficult-to-control hypertension
• Frequent headaches
• Muscle weakness
• Muscle cramps
• Fatigue
• Increased thirst
• Frequent urination
• Numbness or tingling
• Heart palpitations

Some patients discover the condition only after routine blood tests reveal low potassium.

Symptoms of Conn’s Syndrome

Symptoms vary depending on potassium levels and blood pressure severity.

Common symptoms include:

• High blood pressure
• Muscle weakness
• Fatigue
• Muscle cramps
• Excessive urination
• Excessive thirst
• Constipation
• Headaches
• Blurred vision
• Numbness
• Tingling sensations
• Heart rhythm abnormalities
• Difficulty concentrating

Some patients remain completely asymptomatic.

What Is the Hallmark of Conn’s Syndrome?

The hallmark of Conn’s syndrome is persistent high blood pressure caused by excessive aldosterone production together with suppressed renin levels.

Many patients also have low potassium (hypokalemia), although normal potassium levels do not rule out the condition.

Complications

Without treatment, Conn’s syndrome can lead to:

• Stroke
• Heart attack
• Heart failure
• Kidney disease
• Atrial fibrillation
• Left ventricular hypertrophy
• Vision problems
• Persistent hypertension

How Is Conn’s Syndrome Diagnosed?

Early diagnosis is extremely important because the condition is potentially curable.

Doctors combine:

• Clinical history
• Physical examination
• Blood pressure measurements
• Laboratory tests
• Imaging studies

What Are the Lab Findings for Conn’s Syndrome?

Typical laboratory findings include:

• High serum aldosterone
• Low plasma renin activity
• Elevated aldosterone-to-renin ratio (ARR)
• Low blood potassium (in many patients)
• Mild metabolic alkalosis
• Normal or mildly elevated sodium

These findings strongly suggest primary hyperaldosteronism.

What Is the First-Line Investigation for Conn’s Syndrome?

The aldosterone-to-renin ratio (ARR) is the recommended first-line screening test.

It measures:

• Plasma aldosterone concentration
• Plasma renin activity or direct renin concentration

A high ARR indicates inappropriate aldosterone production and warrants further evaluation.

Certain medications may need to be adjusted before testing to improve accuracy.

What Is the Confirmatory Test for Hyperaldosteronism?

If screening tests are positive, doctors usually perform confirmatory testing.

Common confirmatory tests include:

Saline Infusion Test

Intravenous saline is administered over several hours.

Normally, aldosterone levels decrease after saline infusion.

In Conn’s syndrome, aldosterone remains elevated.

Other confirmatory tests include:

• Oral sodium loading test
• Fludrocortisone suppression test
• Captopril challenge test

The choice of test depends on the patient’s clinical condition and local practice.

Imaging Studies

After biochemical confirmation, imaging helps determine the cause.

Doctors may recommend:

• CT scan of the adrenal glands
• MRI (less commonly)

However, imaging alone cannot always determine which adrenal gland is responsible.

Adrenal Vein Sampling

Adrenal vein sampling (AVS) is considered the most accurate method for determining whether excess aldosterone comes from one adrenal gland or both.

This information guides treatment decisions, particularly when surgery is being considered.

Treatment of Conn’s Syndrome

Treatment depends on the underlying cause.

Surgery

Patients with a unilateral adrenal adenoma often benefit from laparoscopic adrenalectomy.

Benefits include:

• Improved blood pressure control
• Reduced need for medications
• Correction of potassium levels
• Possible cure of hypertension in selected patients

Medications

Patients with bilateral adrenal hyperplasia usually receive medications known as mineralocorticoid receptor antagonists, such as:

• Spironolactone
• Eplerenone

These drugs block the effects of aldosterone and help normalise blood pressure and potassium levels.

Lifestyle Changes

Although lifestyle changes alone cannot cure Conn’s syndrome, they support overall treatment.

Recommended measures include:

• Reduce salt intake
• Eat potassium-rich foods if advised by your doctor
• Exercise regularly
• Maintain a healthy weight
• Limit alcohol consumption
• Avoid smoking
• Monitor blood pressure at home
• Take prescribed medications consistently

Prognosis

With appropriate treatment, the outlook for Conn’s syndrome is generally excellent.

Early diagnosis can:

• Improve blood pressure
• Reduce cardiovascular complications
• Protect kidney function
• Improve quality of life
• Lower the long-term risk of stroke and heart disease

Some patients achieve complete cure following surgery, while others successfully manage the condition with medication.

When Should You See a Doctor?

Consult a healthcare professional if you have:

• Blood pressure that remains high despite multiple medications
• Low potassium levels
• Muscle weakness
• Persistent fatigue
• Family history of early hypertension
• Adrenal gland abnormalities
• Early-onset hypertension

Prompt evaluation can identify treatable causes before complications develop.

Frequently Asked Questions (FAQs)

1. What is the cause of Conn’s syndrome?

Conn’s syndrome is caused by excessive production of aldosterone by the adrenal glands. The most common causes are an adrenal adenoma (a benign tumour) and bilateral adrenal hyperplasia, while rare causes include familial hyperaldosteronism and adrenal carcinoma.

2. What is the difference between Conn’s syndrome and hyperaldosteronism?

Hyperaldosteronism refers broadly to any condition with excess aldosterone production. It is divided into:

• Primary hyperaldosteronism (Conn’s syndrome): The adrenal glands themselves produce excess aldosterone, leading to high aldosterone and low renin.
• Secondary hyperaldosteronism: Another condition, such as kidney disease, heart failure, or liver cirrhosis, stimulates excess aldosterone production through increased renin levels.

3. What is the difference between Conn’s and Cushing’s?

Although both disorders involve the adrenal glands, they affect different hormones:

• Conn’s syndrome: Excess aldosterone causes high blood pressure, low potassium, muscle weakness, and increased sodium retention.
• Cushing’s syndrome: Excess cortisol leads to weight gain (especially around the abdomen and face), thinning skin, purple stretch marks, muscle weakness, diabetes, osteoporosis, and mood changes.

4. What is the hallmark of Conn’s syndrome?

The hallmark of Conn’s syndrome is persistent hypertension due to excessive aldosterone production with suppressed renin levels. Low potassium is common but is not present in every patient.

5. What is another name for Conn’s syndrome?

Another name for Conn’s syndrome is primary hyperaldosteronism.

6. What are the lab findings for Conn’s syndrome?

Typical laboratory findings include:

• Elevated serum aldosterone
• Suppressed plasma renin
• High aldosterone-to-renin ratio (ARR)
• Low potassium (in many cases)
• Mild metabolic alkalosis
• Normal or mildly elevated sodium

7. What is the first-line investigation for Conn’s syndrome?

The aldosterone-to-renin ratio (ARR) is the first-line screening test and is considered the most useful initial investigation for detecting primary hyperaldosteronism.

8. What is the confirmatory test for hyperaldosteronism?

The saline infusion test is one of the most widely used confirmatory tests. Other accepted confirmatory tests include the oral sodium loading test, fludrocortisone suppression test, and captopril challenge test.

9. What organ regulates aldosterone?

The kidneys regulate aldosterone production through the renin-angiotensin-aldosterone system (RAAS). Aldosterone itself is produced by the adrenal glands.

10. What are the early signs of high aldosterone?

Early signs include:

• High blood pressure
• Muscle cramps
• Fatigue
• Frequent urination
• Increased thirst
• Headaches
• Muscle weakness
• Heart palpitations

11. What is the main target organ of aldosterone?

The kidneys are the primary target organ of aldosterone, where the hormone promotes sodium and water reabsorption while increasing potassium excretion. Aldosterone also has important effects on the heart and blood vessels.

Conn’s syndrome is one of the most common and treatable causes of secondary hypertension, yet it often goes unrecognised. Because excess aldosterone can damage the heart, kidneys, and blood vessels over time, early detection is essential. If you have resistant high blood pressure, unexplained low potassium, or a family history of early-onset hypertension, speak with your healthcare provider about screening for primary hyperaldosteronism.

Modern diagnostic tests, including the aldosterone-to-renin ratio and confirmatory suppression testing, allow clinicians to identify the condition accurately. Depending on the underlying cause, treatment may involve medication or surgery, both of which can significantly improve blood pressure control and reduce long-term health risks. Early diagnosis and appropriate management offer the best chance of preventing complications and improving overall quality of life.

To consult an Endocrinologist at Sparsh Diagnostic Centre, call our helpline number 9830117733.

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