Secondary aldosteronism differs from primary aldosteronism in that the cause of excess aldosterone is not the adrenal glands, but due to some other problem. Secondary aldosteronism is characterized by reduced renal blood flow, which stimulates the renin-angiotensin system and results in excess aldosterone (because there is not enough blood flow to the kidneys, the body increases aldosterone to boost blood pressure). It has many causes including narrowing of the kidney arteries (i.e., renal arterial stenosis) from atherosclerosis. While in primary aldosteronism, aldosterone will be high while renin is low, in secondary aldosteronism both renin and aldosterone are typically high.
