Additional Information Aldosterone is a mineralocorticoid hormone produced in the adrenal zona glomerulosa under complex control by the renin-angiotensin system. Its action is on the renal distal tubule where it increases resorption of sodium and water at the expense of increased potassium excretion. Thus, syndromes of primary aldosterone excess show hypokalemia. Conversely, increased serum potassium levels act to increase aldosterone output. The principal use for aldosterone measurements is in the diagnosis of primary hyperaldosteronism, which is most commonly caused by a specific type of adrenal adenoma, Conn syndrome.
Secondary aldosteronism is more common.
Work-up is especially indicated in younger patient with hypertension and hypokalemia not induced by diuretic agents. 3 Low plasma renin activity suggests primary aldosteronism and provides indication for aldosterone measurement in a hypertensive subject with renal potassium wasting. 4 High resolution CT is highly accurate for detection of aldosterone-producing adenoma but results must be correlated with endocrine studies. 5 Secondary aldosteronism may occur in congestive heart failure, cirrhosis with ascites, nephrosis, potassium loading, sodium-depleted diet, toxemia of pregnancy and other states of contraction of plasma volume, and Bartter syndrome. Renin is high in secondary aldosteronism, low in primary aldosteronism.