Advantage of a High-Sodium Diet in the Diagnosis of Hyperaldosteronism

Abstract

A metabolic study comprising a diet low in sodium (20-30 mEq/24 h) for three days, then rich in sodium (160-200 mEq/24 h) for five days, was performed on 12 patients who included three cases of primary hyperaldosteronism (proved by measurement of plasma renin and aldosterone in all three cases and confirmed by removal of an adrenal tumour in two cases), four cases of secondary hypermineralocorticism, and five cases of essential hypertension. The effect of the increased sodium intake on the metabolism of potassium allowed a clear difference to be established between primary and secondary hyperaldosteronism. In the former situation, the excretion of potassium rose significantly and kalaemia, already low, dropped even further. In secondary hyperaldosteronism, in contrast, the kaliuria dropped only slightly or not at all, and the kalaemia tended to rise. In essential hypertension there were no systematic variations in potassium excretion and the kalaemia remained within normal limits.

This test, while achieving very useful sodium diet conditions for the measurement of aldosterone and renin in hypertensive subjects with suspected Conn's syndrome, constitutes in itself a method for detecting and establishing a differential diagnosis of hyperaldosteronism in hypertension.

Key words

Hypertension - Conn's Syndrome - Primary Hyperaldosteronism - Secondary Hyperaldosteronism - Sodium Load - Kaliuria - Kalaemia