The predictive value of serum angiotensin-converting enzyme activity in the differential diagnosis of hypercalcemia.

Serum angiotensin-converting enzyme (SACE) activity is usually elevated in sarcoidosis, and this raises the possibility that SACE may be a useful diagnostic tool in distinguishing sarcoidosis from other hypercalcemic disorders. We therefore measured SACE in a large number of patients with various granulomatous, metabolic, and hypercalcemic disorders to determine its predictive value. We found elevated SACE activity in 4 of 35 surgically proven cases of primary hyperparathyroidism and in 3 of 13 patients with oncogenic hypercalcemia. In six patients with sarcoidosis and hypercalcemia, SACE activity was elevated; corticosteroid therapy lowered both the serum calcium and SACE levels to normal. We conclude that SACE activity is not a specific test for the differential diagnosis of hypercalcemia but that it remains useful as a chemical marker of successful treatment of sarcoidosis.