Hypercalcaemia. What does it signify?

Hypercalcaemia can be caused by many disorders, but is most commonly due to primary hyperparathyroidism in outpatients, and to malignant disease in hospital inpatients. When mild (less than 3 mmol/L) it does not cause symptoms, but can have long term effects such as renal calculi. It is important that the aetiology of the hypercalcaemia be established, as it can reflect serious disease. In most patients the correct diagnosis can be suspected from clinical history and examination, and confirmed by laboratory tests and x-rays. The most difficult diagnostic problem is the patient with negative clinical findings, mild hypercalcaemia and mild renal impairment, when the parathyroid hormone level is normal or slightly elevated. When hypercalcaemia is severe (greater than 3.5 mmol/L), it can cause vomiting, polyuria, dehydration and renal impairment, and is then an important therapeutic problem. Therapy includes treatment of the cause, such as radiotherapy for malignant disease or surgery for primary hyperparathyroidism. In addition, it is usually necessary to treat the hypercalcaemia itself, and the initial step is always rehydration. If the plasma calcium concentration remains high, drug treatment must be added, the most effective and reliable agent being intravenous mithramycin. Aminohydroxypropylidene diphosphonate (APD), though less studied, may be equally useful in this situation. Glucocorticoids are not always effective, and phosphate may cause renal damage, particularly when given intravenously. For long term treatment of malignant hypercalcaemia, oral glucocorticoids and phosphate are often effective, and can be given in combination. When primary hyperparathyroidism cannot be corrected surgically, the hypercalcaemia (and hypercalciuria) are probably best treated with a low calcium diet and cellulose phosphate, a regimen also effective for the hypercalcaemia of sarcoidosis.