Hypercalcemia is associated with a few primary
malignant neoplasms and with a variety of
tumors that have spread by
metastases.
Hyperparathyroidism is a diagnosis that is usually not considered in these patients. At our institution, 18 patients with malignant
tumors presented over a 6-year period with
hypercalcemia caused by
hyperparathyroidism. There were five men and 13 women with a mean age of 48 years (range 24-87 years). Primary
tumors in these patients included colon
carcinoma (four cases),
breast carcinoma (four cases),
lymphoma (four cases),
thyroid carcinoma (four cases), Paget's disease (one case), and lung
carcinoma (one case).
Metastases of the primary
tumor occurred in seven patients, and in 11 patients the
tumor was not metastatic or recurrent. Serum levels of
calcium, phosphate, and
chloride averaged 11.8 mg/dl, and 100 mEq/liter, respectively.
C-terminal parathyroid hormone (PTH) levels ranged from 300 to 1,900 pg/ml with an average of 1,150 pg/ml (normal 50-340 pg/ml). At operation, a single
parathyroid adenoma was discovered in 15 patients, and four-gland
hyperplasia was noted in three patients. In all cases, serum levels of
calcium returned to normal after operation. We conclude that patients with malignant
tumors and concomitant
hypercalcemia should be evaluated for the possibility of
hyperparathyroidism. In cases of
primary hyperparathyroidism, elevated
C-terminal PTH level should be diagnostic. If
hyperparathyroidism is determined to be the cause of
hypercalcemia, neck exploration and
parathyroidectomy are indicated.