Primary Aldosteronism (Conn’s Syndrome)
Occasionally a small tumor of the zona glomerulosa cells occurs and secretes large amounts of aldosterone; the resulting condition is called “primary aldostero-nism” or “Conn’s syndrome.” Also, in a few instances, hyperplastic adrenal cortices secrete aldosterone rather than cortisol. The effects of the excess aldosterone are discussed in detail earlier. The most important effects are hypokalemia, slight increase in extracellular fluid volume and blood volume, very slight increase in plasma sodium concentration (usually not more than a 4 to 6 mEq/L increase), and, almost always, hypertension. Especially interesting in primary aldosteronism are occasional periods of muscle paralysis caused by the hypokalemia. The paralysis is caused by a depressant effect of low extracellular potas-sium concentration on action potential transmission by the nerve fibers.
One of the diagnostic criteria of primary aldostero-nism is a decreased plasma renin concentration. This results from feedback suppression of renin secretion caused by the excess aldosterone or by the excess extra-cellular fluid volume and arterial pressure resulting from the aldosteronism. Treatment of primary aldos-teronism is usually surgical removal of the tumor or of most of the adrenal tissue when hyperplasia is the cause.
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