Aldosterone-Renin Ratio ∞ Area

Aldosterone-Renin Ratio

Meaning

The Aldosterone-Renin Ratio (ARR) is a diagnostic calculation from simultaneously measured plasma aldosterone concentration (PAC) and plasma renin activity (PRA) or direct renin concentration (DRC). This ratio assesses the balance between these two key hormones within the renin-angiotensin-aldosterone system (RAAS), primarily screening for primary aldosteronism.

Context

The ARR operates within the renin-angiotensin-aldosterone system, a crucial endocrine pathway regulating blood pressure, fluid balance, and electrolyte homeostasis. Aldosterone, from the adrenal cortex, promotes sodium reabsorption and potassium excretion. Renin, from the kidneys, initiates aldosterone production. Their interplay is vital for systemic physiological stability.

Significance

Clinically, the ARR is the primary screening tool for primary aldosteronism, a common and treatable cause of secondary hypertension. Identifying this condition is critical, as undiagnosed primary aldosteronism increases risk of severe cardiovascular complications like stroke, myocardial infarction, and kidney disease. A high ARR, with elevated aldosterone and suppressed renin, strongly suggests autonomous aldosterone production.

Mechanism

The mechanism hinges on the inverse relationship between aldosterone and renin in primary aldosteronism; excessive adrenal aldosterone production suppresses renin secretion via negative feedback on the renal juxtaglomerular apparatus. In essential hypertension, both hormones are typically proportional. The ratio quantifies this hormonal disproportionality.

Application

In clinical practice, the ARR is applied in the diagnostic workup for patients with resistant hypertension, hypokalemia, or a family history of early-onset hypertension. It is typically performed after careful medication withdrawal and electrolyte correction. The test guides subsequent confirmatory testing, such as saline suppression tests, and lateralization studies for adrenal adenomas.

Metric

The ARR is quantitatively measured from a single blood sample, determining both plasma aldosterone concentration and plasma renin activity or direct renin concentration. Results are commonly expressed in specific units. While diagnostic cut-off values vary, a consistently elevated ratio, especially with low plasma renin, warrants further endocrinological investigation.

Risk

The primary risk is misinterpretation due to factors influencing renin and aldosterone levels, leading to false positives or negatives. Medications like beta-blockers, ACE inhibitors, ARBs, diuretics, and oral contraceptives can significantly alter results, necessitating a careful washout period. Uncorrected hypokalemia also affects aldosterone secretion. Misdiagnosis can delay primary aldosteronism treatment or lead to unnecessary investigations.

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HRTioJuly 22, 2025