Hypercalcaemia: 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

+PassMedicine Notes

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