Primary Aldosteronism: Unilateral or Bilateral Disease?

When you are diagnosed with primary aldosteronism, one of the most critical steps is determining whether the excess aldosterone is coming from one adrenal gland (unilateral) or both (bilateral). This distinction, known as lateralization, strongly influences your treatment plan, though your final path will also depend on your overall health, kidney function, and personal preferences.

In short, unilateral primary aldosteronism is most commonly caused by a single benign tumor on one adrenal gland and can often be treated with surgery ^[1][2]. Bilateral primary aldosteronism means both adrenal glands are overactive; because removing both glands would severely compromise your body’s ability to produce essential hormones, this form is usually treated with long-term medication instead ^[2][3].

Quick Comparison

Unilateral Primary Aldosteronism

Unilateral disease means only one of your two adrenal glands is overproducing aldosterone. This is most commonly caused by an Aldosterone-Producing Adenoma (APA), a small, non-cancerous (benign) tumor that forms on the gland ^[1]. Less commonly, it can be caused by unilateral hyperplasia (enlargement) of just one gland.

If you are a good candidate for surgery and prefer a surgical route, the standard treatment for unilateral disease is adrenalectomy—the surgical removal of the overactive gland ^[2][3]. Medical therapy is an alternative if surgery is not appropriate for you or if you decline it.

Once the abnormal gland is removed, the remaining healthy gland takes over normal hormone production. Surgery often cures the aldosterone excess and normalizes low potassium levels ^[4][5]. However, blood pressure improvement is not guaranteed; many patients still require some blood pressure medication after surgery ^[4][5]. After an adrenalectomy, your doctor will still need to monitor your blood pressure, potassium, and kidney function, as temporary potassium imbalances can sometimes occur post-surgery ^[6][7].

Bilateral Primary Aldosteronism

Bilateral disease means that both of your adrenal glands are overactive and producing too much aldosterone ^[1]. This is most often called Bilateral Idiopathic Hyperaldosteronism (IHA) or bilateral adrenal hyperplasia ^[1]. The tissue in both glands is hyperactive or enlarged rather than there being a single distinct tumor.

Because both glands are malfunctioning, surgery is rarely the standard treatment ^[3]. Instead, bilateral disease is managed with usually long-term, often lifelong, medication—specifically mineralocorticoid-receptor antagonists (MRAs) like spironolactone or eplerenone ^[3][8]. These drugs block the aldosterone hormone from damaging your body, helping to control your blood pressure and correct low potassium ^[9][10].

Medication Side Effects and Monitoring

While MRAs are highly effective, they do not remove the cause of the disease and they require careful monitoring. Because they help your body hold onto potassium, they can sometimes cause your potassium to become too high (hyperkalemia) or worsen kidney function ^[8][11].

Additionally, spironolactone can cause specific side effects, including breast tenderness, breast enlargement (gynecomastia), and menstrual or sexual side effects ^[8][12]. Eplerenone is an alternative that typically avoids these specific sexual side effects, though it can still affect potassium and kidney function ^[12]. Your doctor will routinely check your potassium, kidney function, and renin (a kidney hormone involved in blood pressure balance) to ensure you are on the right dose ^[8][3].

Why not just remove both adrenal glands?

Removing both adrenal glands creates a new, far more dangerous medical condition called adrenal insufficiency ^[13][14].

Your adrenal glands produce several essential hormones besides aldosterone, including cortisol, which helps you respond to stress and illness. If you remove both glands, your body can no longer produce these life-sustaining hormones ^[13]. You would be completely dependent on lifelong glucocorticoid and mineralocorticoid replacement ^[13][14]. In the event of severe physical stress (like an infection or surgery), you would require emergency stress-dosing of steroids or injectable hydrocortisone. Without this, you could experience an adrenal crisis, which is a life-threatening medical emergency ^[15]. Patients who must undergo bilateral adrenalectomy require intense education, emergency plans, and medical alert identification. For routine bilateral primary aldosteronism, medical management with MRAs is much safer ^[3][16].

How Doctors Tell the Difference

Standard imaging, like CT or MRI scans, cannot definitively tell your doctor whether your disease is unilateral or bilateral ^[17]. Small adenomas may not show up on a scan, and harmless, non-functioning nodules are very common, which can mislead doctors into thinking the disease is unilateral when it is actually bilateral ^[17][18].

To confirm whether one or both glands are overactive, specialists often recommend a specialized procedure called Adrenal Venous Sampling (AVS) ^[19]. During AVS, an expert compares the aldosterone and cortisol levels from the veins of each adrenal gland to see where the excess is coming from ^[19][4].

AVS is generally only recommended if you are considering surgery ^[4]. If you and your doctor have already decided that you will treat your condition with medication regardless of the cause, AVS may be unnecessary. Because AVS is a technically demanding procedure, it should be performed at an experienced medical center where the specific risks and limitations can be discussed.