Low Renin Activity in Aldosterone/Renin Ratio Test

Primary Aldosteronism Implications

Primary aldosteronism is characterized by autonomous aldosterone production that is relatively independent of angiotensin II and potassium regulation 1
The condition causes hypertension, cardiovascular/kidney damage, sodium retention, and suppressed plasma renin activity 2
In primary aldosteronism, excessive aldosterone leads to increased potassium excretion which may (but not always) cause hypokalemia 2

A high ARR (typically >30 when aldosterone is measured in ng/dL and renin activity in ng/mL/h) suggests primary aldosteronism 1, 3
Low renin can artificially elevate the ARR even without truly elevated aldosterone levels 4
For a positive ARR test, plasma aldosterone concentration should be at least 10 ng/dL in addition to the elevated ratio 5
The specificity of the ratio improves if a minimum plasma renin activity of 0.5 ng/mL/h is used in calculations 6

Low-renin essential hypertension, a common condition particularly in Black patients, can indicate low renin activity 6
Chronic kidney disease with reduced renin production can also indicate low renin activity 6
Cushing syndrome, which can present with hypertension, hypokalemia, and suppressed renin, is another possible cause of low renin activity 7, 8
Excessive sodium intake or volume expansion states can also lead to low renin activity 6

Confirmatory testing is required, typically with intravenous saline suppression test or oral salt-loading test, when low renin is detected with an elevated ARR 1, 3
Testing should be performed with unrestricted salt intake and normal serum potassium levels 5
Mineralocorticoid receptor antagonists (spironolactone, eplerenone) should be withdrawn at least 4 weeks before testing 5

If primary aldosteronism is confirmed, further evaluation with adrenal venous sampling may be needed to determine if the source is unilateral or bilateral 5
Unilateral aldosterone-producing adenomas may be treated with laparoscopic adrenalectomy 5
Bilateral adrenal hyperplasia is typically treated with mineralocorticoid receptor antagonists 5
Treatment of primary aldosteronism can resolve hypokalemia, lower blood pressure, reduce antihypertensive medication requirements, and improve cardiac and kidney function 5

Not all patients with primary aldosteronism present with hypokalemia - it's absent in the majority of cases 2

The aldosterone-to-renin ratio (ARR) is the recommended screening test for primary aldosteronism, requiring careful interpretation as medications and other factors can influence results, according to the European Society of Cardiology 9

For patients already on antihypertensive medications, the European Society of Cardiology recommends conducting ARR testing without changing medications, interpreting results in context of specific medications the patient is taking, and considering specialist input for interpretation 9
Beta-blockers, centrally acting drugs, and diuretics should be stopped when feasible, while long-acting calcium channel blockers and alpha-receptor antagonists can be used as alternatives as they don't interfere with ARR, as suggested by the European Society of Cardiology 9
Adrenal venous sampling is recommended before surgical treatment to distinguish between unilateral and bilateral disease, as without it, 25% of patients might undergo unnecessary adrenalectomy based on CT findings alone, according to the European Society of Cardiology 10

Medical treatment with mineralocorticoid receptor antagonists is the mainstay of therapy for bilateral disease (Idiopathic Hyperaldosteronism), with the European Society of Cardiology recommending spironolactone as the first-line treatment, and eplerenone as an alternative when spironolactone side effects occur 10