Investigation of incidental hypercalcaemia.

more patients undergoing routine blood tests for other purposes. However, not all cases require treatment. Primary hyperparathyroidism and malignancy together account for 90% of all hypercalcaemic patients.1 Aetiology varies according to the clinical presentation; more indolent cases suggest hyper­ parathyroidism, and more rapidly developing cases suggest malignancy. About 20­30% of all patients with cancer develop hypercalcaemia at some time as a paraneoplastic phenomenon or as a result of bone metastases.2 Dehydration exacerbates underlying hypercalcaemia by reducing renal calcium excretion, and drugs such as thiazide diuretics4 and lithium may exacerbate the underlying hypercalcaemia of primary hyperparathyroidism. The box outlines other causes of hypercalcaemia.