Hypercalcemia: an evidence-based approach to clinical cases.

Primary hyperparathyroidism and malignancy are responsible for greater than 90% of all cases of hypercalcemia. Compared with the hypercalcemia of malignancy, hyperparathyroidism tends to be associated with lower serum calcium levels (< 12 mg/dL) and a longer duration of hypercalcemia (more than 6 months). The hypercalcemic symptoms are usually fewer and subtle. Hyperparathyroidism tends to cause kidney calculi, hyperchloremic metabolic acidosis, and the characteristics of metabolic bone disease osteitis fibrosa cystica, but no anemia. In contrast, hypercalcemia of malignancy is typically rapid in onset, with higher serum calcium levels, and more severe symptoms. Patients so affected show marked anemia, but they never have kidney calculi or metabolic acidosis. Parathyroid hormone assay is the most useful test for differentiating hyperparathyroidism from malignancy and other causes of hypercalcemia. In hyperparathyroidism, serum parathyroid hormone levels will be elevated. In other cases, the high serum calcium concentration usually results in suppression of parathyroid hormone. Treatment of hypercalcemia should be started with hydration. Loop diuretics may be required in individuals with renal insufficiency or heart failure to prevent fluid overload. Calcitonin is administered for the immediate short-term management of severe symptomatic hypercalcemia. For long-term control of severe or symptomatic hypercalcemia, the addition of biphosphonate is typically required. Among intravenous bisphosphonates, zoledronic acid or pamidronate are the agents of choice. Glucocorticoids are effective in hypercalcemia due to lymphoma or granulomatous diseases. Dialysis is generally reserved for those with severe hypercalcemia complicated with kidney failure.