Although
hypercalcemia is a well-known complication of malignant diseases,
hypocalcemia seems to be a rather rare one. A 34-yr-old woman with advanced
breast cancer who presented
hypocalcemia is described. She had generalized multiple osteolytic bone
metastases which were progressive in spite of chemo-endocrine and
radiation therapy. She was admitted because of severe bone
pain and
dyspnea caused by bilateral
pleural effusion. Laboratory examination on admission showed that the serum
calcium was 9.6 mg/dl, serum total
protein 5.9 g/dl, serum inorganic
phosphorus 4.6 mg/dl, and serum
alkaline phosphatase 29.6 King-Armstrong units. The serum
calcium gradually fell to 7.0 mg/dl on the 45th hospital day when the serum total
protein was 6.8 g/dl and she complained of
paresthesia in the extremities. On the 58th day, severe
tachycardia and
hypotension developed and she died of
congestive heart failure on the 67th hospital day. At that time the serum
calcium was 5.4 mg/dl. During her hospital course, the plasma
parathyroid hormone levels were examined repeatedly and were 0.4, 0.6, 0.6 and 0.7 ng/ml (normal; less than 0.5 ng/ml). Autopsy revealed that
cancer invaded the space between the thyroid and the trachea and no parathyroid glands could be found even in the mediastinum. Microscopically the parathyroid glands were replaced completely by the
cancer cells. These observations indicate that
metastasis of
breast cancer to the parathyroid glands caused relative
hypoparathyroidism, resulting in
hypocalcemia. In addition,
congestive heart failure which was refractory to digitalis and
diuretics might have been caused by impaired contractility of the myocardium associated with
hypocalcemia.