Causes

Two conditions account for 90% of cases of hypercalcaemia:

• 1. Primary hyperparathyroidism: commonest cause in non-hospitalised patients
• 2. Malignancy: the commonest cause in hospitalised patients. This may be due to a number of processes, including;
  • PTHrP from the tumour e.g. squamous cell lung cancer
  • bone metastases
  • myeloma,: due primarily to increased osteoclastic bone resorption caused by local cytokines (e.g. IL-1, tumour necrosis factor) released by the myeloma cells
• for this reason, measuring parathyroid hormone levels is the key investigation for patients with hypercalcaemia

Other causes include

• sarcoidosis
  • other causes of granulomas may lead to hypercalcaemia e.g. tuberculosis and histoplasmosis
• vitamin D intoxication
• acromegaly
• thyrotoxicosis
• Milk-alkali syndrome
• drugs:
  • thiazides
  • calcium-containing antacids
• dehydration
• Addison's disease
• Paget's disease of the bone
  • usually normal in this condition but hypercalcaemia may occur with prolonged immobilisation

Management

rehydration with 3 to 4 litres of normal saline