Increased 1, 25-(OH)2D2 Concentration in a Patient with Malignancy-Associated Hypercalcemia Receiving Intravenous Hyperalimentation Inadvertently Supplemented with Vitamin D2

A 55-year-old patient with hypercalcemic crisis due to gastric carcinoma with bone marrow metastasis was treated with bisphosphonate (pamidronate) and calcitonin. Urinary excretion of parathyroid hormone-related protein (PTHrP) was increased. When normocalcemia had been attained, intravenous hyperalimentation was started, in which 1, 000 U vitamin D2 was inadvertently supplemented on days 5-18, On days 15-18, hypercalcemia rapidly recurred, accompanied by markedly increased serum levels of 25-OHD2 (9.1 ng/dl) and 1, 25-(OH)2D2 (161 pg/ml). This clinical course suggests that PTHrP, like PTH, stimulated 1α-hydroxylase activity and produced excessive 1, 25-(OH)2D2. Vitamin D should not be administered to patients with malignancyassociated hypercalcemia, particularly that due to PTHrP-producing tumors.(Internal Medicine 32: 886-890, 1993)