Hypercalcaemia

Patients today are unlikely to present with gross bone disease or severe renal calculi as a consequence of untreated primary hyperparathyroidism. General practitioners who are aware of the telltale signs and symptoms of hypercalcaemia can identify this disorder before gross bone abnormalities or renal problems have had time to develop. The widespread use of multichannel analysers in clinical biochemistry laboratories can detect unsuspected hypercalcaemia even before symptoms become apparent. A high serum calcium concentration may be an unexpected finding in a patient in any clinic or hospital ward, as the symptoms of hypercalcaemia are non-specific. All such findings should be followed up.

Clinical features

Symptoms of hypercalcaemia include:

neurological and psychiatric features such as lethargy, confusion, irritability and depression

gastrointestinal problems such as anorexia, abdominal pain, nausea and vomiting, and constipation

renal features such as thirst and polyuria, and renal calculi

cardiac arrhythmias.

Diagnosis

The commonest causes of hypercalcaemia are primary hyperparathyroidism and hypercalcaemia of malignancy.

A diagnostic decision chart is shown in Figure 36.1. Primary hyperparathyroidism is most often due to a single parathyroid adenoma, which secretes PTH independently of feedback control by plasma calcium. Hypercalcaemia associated with malignancy is the commonest cause of a high calcium in a hospital population. Some tumours secrete a protein called PTHrP (parathyroid hormone-related protein), which has PTH-like properties.