High serum levels of angiotensin-converting enzyme in untreated Addison's disease.

Serum angiotensin-converting enzyme (ACE) in four patients with untreated Addison's disease was significantly higher [79.7 +/- 17.5 (SD) nmol min-1 ml-1] than in normal subjects (37.7 +/- 8.9 nmol min-1 ml-1, P less than 0.02). During corticosteroid hormone replacement therapy the enzyme levels returned within the normal range (44.0 +/- 7.6 nmol min-1 ml-1). In two additional patients the enzyme was assayed only while they were receiving therapy and found normal (38 and 52 nmol min-1 ml-1, respectively). In one of them, an increase ACE level (70 nmol min-1 ml-1) was found after therapy was reduced by 50%. Primary adrenal insufficiency is another disease in which ACE levels may be increased.