Increased Levels of Blood Angiotensin-Converting Enzyme in Idiopathic Hypercalciuric Renal Stone Formers

Dr. L. Radermacher, Department of Nephrology, University Hospital of Liège, Quai G. Kurth, 45, B-4020 Liège (Belgium) Dear Sir, Hypercalciuria is one of the most common causes of recurrent renal stone formation [1]. In some cases, sarcoidosis is the cause of this hypercalciuria [2]. In order to detect patients with sarcoidosis, serum an-giotensin-converting enzyme (ACE) level, a well-known index of disease activity [3, 4], was measured by spectrophotometry assay using hippuryl-histidyl-leucine as substrate [4] in all of our hypercalciuric renal stone formers. Chest radiography, spleen echography and gallium scintigraphy were performed in all patients with increased serum ACE activity in order to confirm sarcoidosis but true sarcoidosis was found in only 2 out of 38 cases. For this reason, we compared, in a short retrospective study, the serum levels of ACE of our idiopathic hypercalciuric renal stone formers to normal subjects. None of our patients had granulomatous diseases or other illness with commonly disturbed levels of serum ACE as hyperthyroidism, lymphoma, diabetes mellitus, renal failure, etc. [4]. Results are given in table 1. Statistical analysis was performed by Student’s t test and χ2 Pearson tests. In normal subjects, ACE was slightly higher in males (p < 0.05), independently of age, as described by Lieberman [3]. Sex ratio was higher in the stone formers group (p < 0.001). Mean serum ACE activity of the stone formers group was statistically higher compared to the normals, especially in males (p < 0.1 between males, p < 0.01 Table 1. Serum ACE activity in idiopathic hypercalciuric renal stone formers and healthy controls (mean ± SD) Controls Idiopathic hypercalciuric p (n ≈ 135) renal stone formers (n = 69) 1.1 NS < 0.001 < 0.1 < O.Ol 44.4 ± 1.6 2.7 30.6 ± 10.4 26.4 ± 7.6 Age, years 42.6 ± Sex ratio (m/f) 1.05ACE activity, nmol/ml/min :6.5 :5.4 Males 23.1: Females 21.2: