The ratio of aldosterone to renin can be an important indicator of conditions like primary aldosteronism. Find out how doctors test this ratio and how to interpret results.
What is Aldosterone?
Aldosterone is a hormone produced in the adrenal glands. It is a key component along the renin-angiotensin-aldosterone-system (RAAS) axis, an endocrine system that helps regulate blood pressure, electrolytes and fluids. When activated, aldosterone causes the body to hold onto more salt and water, causing blood pressure to go up.
However, despite its key role in regulating blood pressure, aldosterone can sometimes be overproduced in the body independent of signals from the RAAS. Detecting high amounts of aldosterone is the first step toward diagnosing primary aldosteronism. High aldosterone levels can also lead to low plasma potassium levels.
A rise in blood aldosterone levels causes secondary hypertension, which is usually difficult to treat. Secondary hypertension caused by primary aldosteronism differs from essential hypertension (also called primary hypertension). Essential hypertension isn’t caused by a medical condition. Aldosterone overproduction is sometimes the result of an adenoma causing hyperactivity and high aldosterone.
An estimated 1.5% to 5% of hypertensive patients globally with primary aldosteronism have an adenoma. Possible causes of primary aldosteronism and increased aldosterone in the blood include bilateral adrenal hyperplasia or even malignant cancerous tumors.
Because another medical condition causes secondary hypertension, it can be more challenging to treat. In fact, patients often take multiple hypertension medications to keep aldosterone in check. Hypertension that is difficult to treat can lead to a range of complications, including heart disease and chronic kidney disease (CKD).
What is Renin?
Renin is an enzyme produced by the kidneys that plays an important role in managing blood pressure. In fact, renin kickstarts the body’s RAAS system.
When blood pressure gets too low, and the RAAS is activated, the kidney secretes renin into the bloodstream. The presence of renin causes a cascade of signaling reactions: renin converts to angiotensin I, which triggers the production of angiotensin II, which facilitates the production of aldosterone. The presence of aldosterone forces the body to hold on to more salt and water. As a result, blood pressure goes up. In other words, the secretion of renin causes blood pressure to rise.
What is the Aldosterone to Renin Ratio?
The aldosterone to renin ratio refers to the amount of aldosterone in the blood compared to the amount of renin. Normally, this ratio is relatively balanced because the RAAS maintains an equilibrium between the two. That’s because, in the RAAS, more renin activity leads to increased aldosterone production. Once the body produces aldosterone, helping restore normal blood pressure, renin activity reduces, signaling that less aldosterone is needed.
However, in people with primary aldosteronism, aldosterone is overproduced independent of signals from the RAAS. As a result, aldosterone remains high even if renin has become less active, changing the ratio of aldosterone to renin.
What Factors Affect the Aldosterone to Renin Ratio?
Several factors can affect the aldosterone to renin ratio. These include changes in dietary salt intake, pregnancy and stress. Taking certain medications for hypertension can also affect the balance between aldosterone and renin. Common medications for treating primary aldosteronism (such as mineralocorticoid receptor antagonists (MRAs) that target aldosterone production) can cause low aldosterone levels.