Calcium homeostasis is primarily controlled by parathyroid hormone and hydroxylated vitamin D. Parathyroid hormone is produced by the parathyroid gland and vitamin D is either indigested in the diet or synthesized in the skin via exposure to sunlight. The mechanisms of action are outlined in the diagram below:
Hypercalcaemia can result in the following signs and symptoms (beyond the classical ‘stones, bones, abdominal groans and psychic moans…’)
- Polyuria
- Polydipsia
- Renal stones
- Nausea and vomiting
- Anorexia
- Constipation
- Confusion
- Psychotic behaviour
- Headache
- Bone pain
- Hypertension (rare)
Causes of hypercalaemia:
- Main causes (>90%)
- Primary hyperparathyroidism
- Malignant disease
- Other causes
- Sarcoidosis
- Immobilisation
- Vitamin A or D toxicity
- Drugs – thiazide, lithium
- Thyrotoxicosis
- Addisons
- Phaeochromocytoma
- Granulomatous disease –TB, Wegeners granulomatosis, histoplasmosis
- Milk-alkali syndrome
Malignant disease can cause hypercalcaemia due to:
- Bone involvement – boney mets - ‘bronchus, breast, byroid, brostate and bidney’ (AKA bronchus, breast, thyroid, prostate and kidney) and myeloma
- Parathyroid Hormone related Peptide (PTHrP) produced by tumour, especially squamous cell tumours such as lung, oesophagus and breast, renal and bladder tumours.
ECG changes seen in hypercalcaemia can include: short QT, bradycardia, bundle branch block or AV block
Treatment is:
- Treat cause
- Normal saline
- Pamidronate
Small print gem: Hypercalcaemia increases sensitivity to digoxin
References:
