Conn Syndrome (Primary Aldosteronism)

What aldosterone does

Aldosterone is made by the outer layer of the adrenal glands. It signals the kidneys to hold on to sodium and water and to excrete potassium. Normally, the kidney's renin-angiotensin system controls how much aldosterone is made. In primary aldosteronism, the adrenal gland makes aldosterone on its own, so renin is suppressed while aldosterone stays high. The result:

• salt and water retention, raising blood pressure
• potassium loss in urine, sometimes causing low blood potassium (hypokalemia)
• direct damaging effects of aldosterone on the heart, blood vessels and kidneys

Causes

Familial hyperaldosteronism, including a glucocorticoid-remediable form, runs in families and can cause severe hypertension at a young age.

Symptoms

Many people have no symptoms apart from high blood pressure, which is why screening matters. When potassium is low, symptoms can include:

• muscle weakness, cramps or spasms
• tiredness
• passing large amounts of urine, including at night, and thirst
• palpitations
• headaches
• tingling, and rarely temporary paralysis

Only a minority of people with primary aldosteronism have low potassium, so a normal potassium does not rule it out.

Who should be screened

Guidelines recommend testing people with:

• blood pressure above about 150/100 mm Hg on repeated readings
• hypertension needing 3 or more medicines, or uncontrolled on 3
• high blood pressure with spontaneous or diuretic-induced low potassium
• high blood pressure and an adrenal nodule found on a scan
• high blood pressure with sleep apnea
• high blood pressure with atrial fibrillation
• high blood pressure with a family history of early-onset hypertension or stroke before age 40
• first-degree relatives of people with primary aldosteronism

Recent guidance increasingly supports screening everyone with high blood pressure at least once.

Diagnosis

1. Screening: a morning blood test for aldosterone and renin, expressed as the aldosterone-to-renin ratio. Low potassium is corrected first. Some blood pressure medicines affect results, and your doctor may adjust them.
2. Confirmation: in many cases, a suppression test, such as a saline infusion or oral salt loading, checks whether aldosterone stays high when it should fall. Very clear-cut results may not need this step.
3. Adrenal CT scan: looks for an adenoma and excludes adrenal cancer.
4. Adrenal vein sampling: a radiologist samples blood from both adrenal veins to show whether one or both glands are producing the excess. This is needed before surgery in most adults, because small adenomas may not show on CT and incidental nodules may not be the source.

Treatment

One-sided disease

Laparoscopic adrenalectomy, keyhole removal of the affected adrenal gland, corrects low potassium in nearly everyone and cures or improves blood pressure in most people. Around a third to half no longer need blood pressure medicines; others need fewer.

Both-sided disease or if surgery is not suitable

Mineralocorticoid receptor antagonists block aldosterone's effects:

• Spironolactone: effective and inexpensive. Side effects include breast tenderness or enlargement in men and menstrual changes in women.
• Eplerenone: fewer hormonal side effects, but needs twice-daily dosing.

Other blood pressure medicines can be added. Potassium levels and kidney function are monitored. Salt restriction helps.

Complications

Compared with people who have the same blood pressure from other causes, those with untreated primary aldosteronism have higher rates of:

• stroke and heart attack
• atrial fibrillation
• heart failure and thickening of the heart muscle
• chronic kidney disease

Targeted treatment reduces these risks.

Frequently asked questions

What is Conn syndrome?

Conn syndrome is the original name for primary aldosteronism caused by a benign adrenal tumor that makes too much aldosterone. Today the term often covers all forms of primary aldosteronism. It causes high blood pressure and sometimes low potassium, and it is often curable.

What are the symptoms of primary aldosteronism?

Many people only have high blood pressure, often hard to control. If potassium is low, there may be muscle weakness, cramps, tiredness, palpitations, frequent urination and thirst. Most people with the condition have normal potassium.

How is Conn syndrome diagnosed?

It starts with a blood test comparing aldosterone and renin levels. If the ratio is high, confirmatory tests, an adrenal CT scan and often adrenal vein sampling show whether one or both adrenal glands are responsible, which determines treatment.

Can Conn syndrome be cured?

Yes, when only one adrenal gland is responsible. Removing that gland corrects potassium in nearly all people and lowers blood pressure in most, sometimes curing hypertension completely. When both glands are involved, medicines such as spironolactone control the condition well.