Calcium and phosphorus studies: interpretation of results and strategies for further testing.

Persistent hypercalcemia is most often due to tumor. Other causes are best eliminated by clinical methods combined with simple tests. Hypocalcemia is most often a result of hypoalbuminemia. Hyperphosphatemia induced by phosphate infusion or enema may cause profound hypocalcemia. Biochemical profiling may uncover severe hypophosphatemia necessitating phosphate administration. Markedly elevated serum alkaline phosphatase in the absence of hepatic disease is most likely to reflect either Paget's disease of bone or metastatic prostate cancer.