The Significance of Elevated Levels of Plasma 18-Hydroxycorticosterone in Patients with Primary Aldosteronism*

Plasma 18-hydroxycorticosterone (18OHB) concentration was measured in 23 patients with primary aldosteronism. After overnight recumbency, the levels were markedly elevated and were 6 times higher in patients with aldosteroneproducing adenomas than in patients with hyperplasia. A value of 100 ng/dl or greater at 0800 h after overnight recumbency distinguished an adenoma from hyperplasia. There was no overlap of values, as was observed with plasma aldosterone concentration (PAC) at 0800 h and after 4 h of upright posture at 1200 h. There was a significant negative correlation between the ratio of 18OHB to PAC and the potassium concentration in patients with primary aldosteronism due to hyperplasia. Potassium repletion with potassium chloride and/or spironolactone in patients with aldosterone-producing adenomas decreased the 18OHB:PAC ratio by decreasing 18OHB and increasing PAC. 180HB is an effective discriminator of an adenoma and may be a useful marker of the events in late aldosterone synthesis.