Hyperaldosteronism occurs when your adrenal glands produce too much aldosterone, a hormone that regulates blood pressure by managing sodium and potassium levels. Excess aldosterone leads to an electrolyte imbalance, often resulting in high blood pressure.
Why and When Testing is Recommended
Testing for hyperaldosteronism is important because it’s a treatable cause of high blood pressure, especially resistant hypertension—blood pressure that remains elevated despite multiple medications. Up to 20% of patients with resistant hypertension may have primary hyperaldosteronism. Identifying this underlying hormonal imbalance can lead to more effective treatment strategies.
Screening is also recommended for those with hypertension and persistently low potassium (hypokalemia), though many with hyperaldosteronism have normal potassium. Other groups who should consider testing include people with early-onset or severe hypertension, a family history of early-onset hypertension or stroke, or an incidental adrenal mass found on imaging.
Initial Diagnostic Steps
Diagnosis typically begins with the Aldosterone-Renin Ratio (ARR) blood test. This measures plasma aldosterone concentration (PAC) and plasma renin activity (PRA) or concentration (PRC). In hyperaldosteronism, aldosterone is elevated while renin, which normally stimulates aldosterone, is suppressed. A high ARR suggests the condition.
Proper preparation is crucial for accurate results, as certain medications and dietary factors can influence hormone levels. You may need to stop specific blood pressure medications, such as spironolactone, eplerenone, or potassium-wasting diuretics, for at least four weeks. Other medications, including beta-blockers and ACE inhibitors, might also require adjustment or temporary discontinuation. It is also important to maintain a normal sodium intake and ensure potassium levels are within the normal range, as hypokalemia can suppress aldosterone secretion. Blood samples are usually collected mid-morning after you have been upright for at least two hours and seated for 5-15 minutes.
Confirming the Diagnosis and Locating the Source
If the Aldosterone-Renin Ratio suggests hyperaldosteronism, confirmatory tests are performed to assess if aldosterone production can be suppressed, which would normally occur in individuals without the condition. Common options include:
Saline Infusion Test: Two liters of 0.9% saline solution are administered intravenously over four hours. Blood samples are taken before and after; in hyperaldosteronism, aldosterone will not suppress as expected.
Oral Salt Loading Test: Dietary sodium intake is increased for three days, followed by a 24-hour urine collection. Persistent high urinary aldosterone despite adequate salt intake indicates the condition.
Fludrocortisone Suppression Test: Fludrocortisone, a mineralocorticoid, is taken for four days, along with salt and potassium supplements, to see if it suppresses aldosterone production. This test is highly accurate but more cumbersome and often requires hospitalization.
Once hyperaldosteronism is confirmed, imaging studies are used to locate the source of the aldosterone overproduction. A computed tomography (CT) scan of the adrenal glands is typically performed to look for a tumor (adenoma) or bilateral adrenal hyperplasia (enlargement of both adrenal glands). While a CT scan can identify larger tumors, it may miss smaller ones, and the presence of a nodule does not always confirm it is the source of excess hormone.
Adrenal Vein Sampling (AVS) is considered the gold standard for accurately determining whether one or both adrenal glands are overproducing aldosterone. This minimally invasive procedure involves inserting a catheter to sample blood directly from the veins draining each adrenal gland and a peripheral vein. By comparing aldosterone levels, AVS can differentiate between a unilateral source (one gland) and bilateral overactivity (both glands), which is crucial for guiding treatment decisions.
Interpreting Your Results
Interpreting the various test results requires careful evaluation by a healthcare professional, often an endocrinologist or hypertension specialist. For the initial Aldosterone-Renin Ratio, a high ratio with elevated aldosterone and suppressed renin generally suggests hyperaldosteronism, though specific cut-off values can vary between laboratories. Confirmatory tests provide further evidence that aldosterone secretion cannot be appropriately suppressed. If your aldosterone levels remain high after tests like the Saline Infusion or Oral Salt Loading, it confirms autonomous aldosterone production, meaning your adrenal glands are producing aldosterone independently of normal regulatory signals.
The findings from localization studies, such as CT scans and especially Adrenal Vein Sampling, guide the next steps in management. If AVS shows that only one adrenal gland is overproducing aldosterone, surgical removal of that gland may be a highly effective treatment option. Conversely, if both glands are found to be overactive, medical management with aldosterone-blocking medications is typically recommended. Your doctor will discuss these results with you and determine the most appropriate treatment plan for your specific condition.