When doubt as to the cause persists, a hydrocortisone suppression test may be helpful. Should the calcium revert to normal when hydrocortisone (40 mg, 8 hourly for ten days) is given, then hyperparathyroidism is a very unlikely cause of the hypercalcaemia. Failure to suppress does not, however, prove the diagnosis of hyperparathyroidism since 50% of cases of hypercalcaemia of malignancy fail to suppress.
