Hypocalcemia in metastatic bone disease: Metabolic and radionuclide studies of a case
Tomography, Emission-Computed, Single-Photon
A patient with refractory hypocalcemia, associated with metastatic bone disease, was studied. Greater than 7,000 mg of elemental calcium plus 50,000 IU of vitamin D daily, were required to raise serum calcium levels. Amino-terminal and carboxy-terminal parathyroid hormone and urinary cyclic AMP levels were inappropriately low, while calcitonin levels were unexpectedly elevated. Reduced 1,25(OH)2 vitamin D with normal 25 (OH) vitamin D levels were found. A 24-hour study of (99m)Tc pyrophosphate retention provided evidence of enhanced skeletal avidity for calcium in this setting. We conclude that hormonal or local tumor-related factors created a profound calcium demand in a setting of impaired homeostatic mechanisms. An unusually severe and resistant form of hypocalcemia resulted.