Today in Medicine: SALT study questions prevalence of undiagnosed primary hyperaldosteronism among patients with low-renin hypertension

July 9, 2007 By Benjamin A. Olenchock, M.D. Ph.D. [mailto:bolenchock@partners.org]

Cambridge, UK Taking a pragmatic approach to address the disease burden of primary hyperaldosteronism (PHA), investigators at the University of Cambridge have demonstrated that a thiazide diuretic is just as effective as spironolactone for blood pressure control in patients with low-renin hypertension who have an elevated aldosterone-renin ratio.

Hypertension due to classic PHA presents with elevated aldosterone, low renin, and hypokalemia. Recent work has suggested that an elevated aldosterone-renin ratio can help identify undiagnosed PHA in low-renin hypertensives with normal serum potassium. The SALT study questioned the prevalence of this population.

Their study, to be published in the journal Circulation, was a double blind, placebo-controlled, randomized crossover study comparing bendroflumethiazide to spironolactone. Fifty-seven patients were selected based on hypertension, low renin level, elevated aldosterone-renin ratio, and previous blood pressure response to spironolactone. The authors hypothesized that if PHA were prevalent among this patient population, then spironolactone would be superior for blood pressure control.

The low-dose comparison demonstrated that spironolactone 50 mg was in fact superior to bendroflumethiazide 2.5 mg for blood pressure control (change in SBP -10.1 vs. -4.9, p=0.005). However, the higher dose comparison demonstrated that spironolactone 100 mg showed no benefit over bendroflumethiazide 5 mg in its effect on SBP (-11.6 vs -10.5, p=0.44). Spironolactone treatment was statistically superior for the secondary measures of natriuresis and reversal of renin suppression.

These results support the view that undiagnosed PHA is likely rare among low-renin hypertensives. The authors question the utility of the aldosterone-renin ratio and need for expensive search for adrenal adenomas in low-renin hypertensives with normal serum potassium.

The trial was funded by the British Heart Foundation.


 * 1) ref1 pmid=17606839