Functional derangements in the regulation of aldosterone secretion in hypertension

Excess production of aldosterone secondary to an adrenal tumor or bilateral hyperplasia is a known, but infrequent, cause of hypertension. A more frequent adrenal abnormality, observed in 30-40% of hypertensive patients, is a functional derangement in aldosterone secretion. Two such conditions have been described: low renin essential hypertension and non-modulating essential hypertension. Both have in common 1) an abnormality in the interaction of angiotensin II (Ang II) with the adrenal and 2) sodium sensitivity of the blood pressure. However, the pathophysiological mechanisms for the sodium sensitivity and hypertension are different. In normal subjects, the response of the adrenal glomerulosa cell to Ang II varies with the level of sodium intake, with sodium restriction enhancing the response. In one group of hypertensive patients with low plasma renin levels, the normally reduced aldosterone responses to Ang II on the high salt diet do not occur. Thus, these individuals have an enhanced adrenal response to Ang II under circumstances in which it should be reduced, thereby leading to lower renin levels and a tendency toward sodium retention. The second group has the opposite defect; that is, on a low sodium diet, they have a reduced adrenal response to Ang II. This results in a normal or high plasma renin level. The sodium sensitivity of their blood pressure arises not from the adrenal abnormality but from the associated defect in sodium-dependent, Ang II-mediated changes in renal blood flow. Thus, on a high salt diet, these patients, who are termed "non-modulators," fail to increase renal blood flow, thereby leading to a sodium-retaining state.(ABSTRACT TRUNCATED AT 250 WORDS)