Hypocalcaemia
Overview
Hypocalcaemia refers to a reduced serum calcium concentration. This may occur due to disorders related to parathyroid hormone, vitamin D or bone metabolism.
Look For
- Total calcium <2.15 mmol/L
- Ionised calcium < 1.15 mmol/L
Aetiology
Causes of Hypocalcaemia
- Hypoparathyroidism - iatrogenic, autoimmune, congenital
- PTH resistance - pseudohypoparathyroidism, hypomagnesaemia
- Vitamin D deficiency - inadequate intake, low sun exposure, malabsorption, liver failure, chronic kidney disease
- Increased excretion / reduced bony turnover - loop diuretics, osteoporosis, cachexia, bisphosphonates, malignancy
- Extravascular calcium buildup - osteoblastic metastases, sepsis, pancreatitis
- Calcium chelation - alkalosis, citrate, EDTA, hyperphosphataemia
- Genetic - familial hypoparathyroidism, DiGeorge syndrome
Clinical Features
Signs and Symptoms
- Hyperreflexia
- Tetany (Chvostek's & Trousseau's signs)
- Seizures
- Heart failure (due to reduced contractility)
ECG Changes
- Prolonged QT
- Torsade de pointes (rare, even with severe hypocalcaemia)
Approach
Check the patient's PTH, phosphate, vitamin D and magnesium levels. If a cause is not evident and hypocalcaemia is ongoing (i.e. not lab error) then further investigation may be warranted.
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