Endocrine

Hypocalcaemia

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Pathology

Very common in hospital patients. Low Ca2+ interferes with the function of neurones and cardiac and skeletal myocytes.

Aetiology

Low PTH:
Hypoparathyroidism - primary or iatrogenic
High PTH (secondary hypoparathyroidism):
Vitamin D deficiency
PTH resistance (pseudohypoparathyroidism, hypomagnesaemia)
Rickets
Fanconi’s syndrome
Normal PTH:
Drugs – blood transfusion, bisphosphonates, phenytoin, ketoconazole, 
Acute pancreatitis
Toxic shock syndrome
Hyperventilation
Rhabdomyolysis
Tumour lysis syndrome or sclerotic bone metastases.

Signs

Chvostek’s sign (tapping over facial nerve produces spasm)
Trousseau’s sign (inflation of BP cuff causes carpopedal spasm). 
If chronic can cause abnormal dentition, subcapsular cataract, papilloedema, confusion, ectopic calcification.

Symptoms

Paraesthesia, muscle cramps and spasms, tetany

Investigations

Bloods: Corrected Ca2+, PTH, U&E, Mg2+, phosphate, CK (rhabdomyolysis),
amylase (pancreatitis)
ECG: Prolonged QT and ST intervals
Imaging: Renal ultrasound, ultrasound neck, SestaMIBI of parathyroids, bone 
scan for metastases

Treatment

Acute: Calcium gluconate IV. If hypomagnesaemia correct this concurrently.
Chronic: Supplement vitamin D, oral calcium supplements, adequate dietary 

Prognosis

Dependant on cause, some will have unstable calcium levels long term..
Arrhythmias, prolonged QT interval on ECG, laryngospasm, bronchospasm.

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