To the Editor.
—The article by Smallridge et al1 in the Archives and a previous one by the same authors2 might create the impression that there exists a causal linear relationship between serum angiotensin I—converting enzyme (SACE) activity and thyroid hormone levels. In a group of patients with hyperthyroidism, I found an increased number of cases with an elevated SACE activity but found no significant linear relationship between SACE levels and thyroid hormone levels in the blood (unpublished data, 1985). Furthermore, among cases of hypothyroidism, I found that some patients had markedly elevated SACE levels but that the rest had values in the reference range.Many other studies have reported that in many unrelated diseases a substantial portion of patients exhibited elevated levels of SACE.3 This group of diseases included sarcoidosis, diabetes mellitus, Gaucher's disease, leprosy, histoplasmosis, and liver cirrhosis. Although these diseases are seemingly unrelated, there