DOCA test for aldosteronism: its usefulness and implications.

Experience with the DOCA test (measurement of urinary excretion of aldosterone before and after 3 days of administration of 10 mg deoxycorticosterone acetate [DOCA] intramuscularly every 12 hours while on high sodium intake) is presented in 129 hypertensive patients to define its usefulness in discriminating between autonomous and nonautonomous production of aldosterone. All patients who did not have primary aldosteronism had a decrease in urinary excretion of aldosterone to values within the normal range, with a greater than 30% fall from control values. Patients with an aldosterone-producing adenoma had a 5.7% fall and those with idiopathic hyperaldosteronism had a 9.9% fall. Sodium retention was limited in these patients when compared with that in normal subjects. The least retention occurred in patients with an aldosterone-producing adenoma, whereas patients with low-renin essential hypertension retained more sodium than any other hypertensive group; the latter required greater sodium retention than those with normal-renin essential hypertension to produce a similar decrease in urinary aldosterone. Sodium retention correlated significantly with the percent fall in urinary aldosterone only in the low-renin essential hypertension group. Serum potassium levels fell in all groups. Changes in serum potassium levels and plasma renin concentration did not correlate with changes in urinary aldosterone excretion. The DOCA test is effect in discriminating between primary aldosteronism and other causes of hypertension. It also demonstrates that in hypertensive patients small changes in sodium retention reduce aldosterone excretion.