Treatment of hypercalcemia.

Severe hypercalcemia is a potentially life-threatening complication of several diseases. Most commonly it is caused by cancers that enhance bone resorption. Impaired renal calcium excretion resulting from a combination of volume contraction and calcium-induced renal injury (nephrocalcinosis) plays a critical role in the genesis and aggravation of hypercalcemia. Treatment of hypercalcemia is based on treating the underlying disease, restoring extracellular volume, correcting electrolyte deficiencies (potassium and magnesium), and reducing bone resorption. Several measures are available to reduce bone resorption, of which the most efficacious are the bisphosphonates and plicamycin (mithramycin). One of these agents in combination with volume expansion can reduce serum calcium concentrations to near normal in most patients within 3 to 6 days. Because of the delayed hypocalcemic action of these agents, they should be administered early. Calcitonin has a more modest hypocalcemic action than the bisphosphonates or plicamycin but has a more rapid effect. Combining calcitonin with plicamycin or a bisphosphonate can enhance the rate of decline of the serum calcium level. Bone resorption also can be reduced by getting patients out of bed to stand or walk. Glucocorticoids may be effective in patients with hypercalcemia associated with high levels of vitamin D, such as sarcoidosis, some lymphomas, or vitamin D intoxication. Patients with mild to moderate hypercalcemia may be asymptomatic. Therapy in these patients should be directed at the primary disease as well as at preventing complications that could raise the level of serum calcium. Efforts should be made to prevent volume contraction and prolonged bed rest. Sedatives and narcotic analgesics, by reducing activity and oral intake, can raise serum calcium levels. In the future it may be possible to predict which patients with cancer are likely to develop accelerated local tumor-mediated or humorally mediated osteolysis. For example, high circulating levels of PTH-like peptides in patients with lung cancer might suggest a greater risk of developing hypercalcemia. These patients could be monitored more closely by periodically measuring urinary calcium. Another prophylactic approach would be to treat patients at risk of developing hypercalcemia with drugs, such as the bisphosphonates, that inhibit bone resorption.