EVIDENCE THAT PRIMARY ALDOSTERONISM MAY NOT BE UNCOMMON - 12-PERCENT INCIDENCE AMONG ANTIHYPERTENSIVE DRUG TRIAL VOLUNTEERS

1. Six (12%) out of 52 respondents to newspaper advertisements for ant ihypertensive drug trials had elevated aldosterone to renin ratio, con firmed by repeated measurement. 2. Failure to suppress aldosterone wit h fludrocortisone acetate administration and oral salt loading confirm ed the presence of primary aldosteronism in all six patients. 3. Two o f the six patients have already had aldosterone-producing adenomas rem oved, one has commenced spironolactone, and one has an adrenal mass on computerized tomography but investigation is incomplete. 4. None of t he six patients with primary aldosteronism had unprovoked hypokalaemia . 5. Plasma aldosterone levels did not distinguish those patients with subsequently proven primary aldosteronism from the others. Plasma ren in activity (PRA) was a better discriminator, but not as good as the a ldosterone to renin ratio.6. The incidence of primary aldosteronism is probably much higher than the 1% currently quoted in texts, with earl ier, normokalaemic forms accounting for the majority of cases.