Coexistent Hyperparathyroidism and Thyroid Disease

To the Editor.—  It has always been our practice to determine serum calcium levels in patients who have undergone thyroid surgery to exclude the possibility of postsurgical hypoparathyroidism. In three cases, however, we were surprised to find hypercalcemia, after thyroid surgery, later demonstrated to be previously undetected hyperparathyroidism. We apprehensively advised parathyroid surgery in these three cases, knowing quite well that the risk of an unsuccessful operation is greater in patients with prior neck surgery. In one case, we elected to do parathyroid catheterization studies with differential parathyroid hormone determinations to accurately localize the lesion prior to surgery because the patient had severe angina. Fortunately, all three patients had successful parathyroid surgery with resumption of normal calcium values.Because of this experience, we have recently started to determine serum calcium values in all patients with thyroid nodules to exclude possible coexisting hyperparathyroidism prior to thyroid surgery. Recently, we encountered a