Clinical manifestations of cancer-related hypercalcemia.

Hypercalcemia is a potentially lethal endocrine disorder occurring in 10% to 20% of cancer patients at some time during the course of their disease. Clinical manifestations vary in severity, depending on the degree and duration of hypercalcemia, rapidity of onset, patient's age, performance status, sites of metastases, previous antineoplastic therapy, and the presence of hepatic or renal dysfunction. The clinical features of hypercalcemia are protean and affect multiple organ systems, resulting most prominently in neurologic, gastrointestinal, renal, cardiovascular, and musculoskeletal morbidity. Recognition of the disorder requires a high index of suspicion because many of its symptoms, such as nausea, anorexia, weakness, fatigue, lethargy, and confusion, are non-specific and, in the patient with a malignancy, can result from other complications of the primary disorder. If identified appropriately as being related to hypercalcemia, such symptomatology is potentially reversible with treatment. Whereas in the ambulatory general medical population the most common cause of hypercalcemia is primary hyperparathyroidism, in cancer patients and hospitalized patients in general, the most common cause is malignancy. Hypercalcemia in cancer patients is, in most cases, due to advanced metastasized disease. Diagnostic tests are useful in the differential diagnosis of hypercalcemia, and such tests, together with an accurate history and careful clinical observation, permit the best therapeutic approach to an individual patient.