Humoral nonparathyroid hypercalcemia without evidence of bone involvement

A case of humoral non-parathyroid hypercalcemia in a breast cancer patient is discussed. Bone metastases developed 23 months after the first clinical evidence of increased serum calcium levels and did not appear to be etiologically involved in this case of hypercalcemia. Serum levels of I-PTH and PGE2 were normal, as were urinary c-AMP levels. Furthermore, no significant response to corticosteroid therapy was observed. However, the correlation between the activity of metastatic disease and calcemia suggests that this cancer produced humoral factor(s) with calcium-mobilizing activity.