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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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