Measurement of the End‐Organ Responses to Aldosterone in Man: Diversity of Response and its Possible Biological Significance

Abstract

Summary: The renal (potassium and sodium ratios) and rectal (potential difference) response to an infusion of aldosterone were measured in 13 hypertensive subjects. The correlation between these two responses was highly significant though the magnitude of the response varied widely between subjects. The variation in response between subjects showed no correlation with the change in, or maximal plasma level of, aldosterone and was thus thought to reflect a diversity in the end‐organ response to aldosterone between subjects.Biological significance of the diversity of response is suggested by the closer correlation between aldosterone excretion and aldosterone effect when the individual's particular responsiveness to aldosterone is taken into account. Thus the 24‐hour urine K+/Na+ (as a measure of the aldosterone effect) shows a relatively poor correlation with 24‐hour urine aldosterone excretion (r = 0·63, P > 0·05). Compared with this, the 24‐hour urine K +/N/a+ shows an improved correlation with the product of the 24‐hour urine aldosterone factored by an index of the individual's responsiveness (r = 0·83, P < 0·01).The diversity of end‐organ responsiveness makes interpretation of “normal” aldosterone levels difficult, and may explain some cases where there is evidence suggestive of hyper‐aldosteronism with “normal” levels of aldosterone. To examine such a possibility, one such case of a patient with hypertension, “normal” but non suppressible aldosterone excretion and episodic hypokalaemia is presented in detail.