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Electrolyte Abnormalities




Hypercalcaemia, or an increased serum calcium concentration >2.60 mmol/L, shortens action potentials which primarily results in early ventricular repolarisation (shortened QT) on ECG.


  • Causes of Hypercalcaemia

  • Malignancy - local osteolysis, humoral hypercalcaemia of malignancy, multiple myeloma
  • Hyperparathyroidism (primary / secondary / tertiary)
  • Endocrine - thyrotoxicosis, Addison’s disease
  • Granulomatous disease - sarcoidosis, tuberculosis
  • Prolonged immobilisation
  • Drugs - calcium supplements, vitamin D, vitamin A, thiazides, lithium, oestrogens, anti-oestrogens, progestins
  • Total parenteral nutrition (TPN)
  • Familial hypercalcaemia-hypercalciuria (FHH)


  • Signs and Symptoms

  • Renal (‘stones’) - nephrolithiasis, nephrocalcinosis, nephrogenic diabetes insipidus
  • GI (‘groans’) - nausea, reflux, peptic ulcers, pancreatitis, constipation
  • CNS (‘moans’) - lethargy, depression, confusion, memory loss, coma
  • MSK (‘bones’) - osteopaenia, bone pain, pathologic fractures
  • Cardiovascular - hypertension, shortened QT


  • Bloods

  • Total calcium >2.60 mmol/L
  • Ionised calcium >1.35 mmol/L
  • ECG Findings

  • Shortened QT interval (due to a shortened ST segment)
  • Osborn waves (J waves) - dome or hump-shaped deflections following the J point
  • QRS prolongation
  • PR prolongation
  • Diagnosis
Severe hypercalcaemia may produce ST elevation and T wave inversion that mimics an acute myocardial infarction.
  • Further Investigations

  • Check the patient’s PTH
  • If not elevated - check the PTH-related peptide (PTHrp), 25-hydroxy-vitamin D and 1,25-dihydroxy-vitamin D levels
  • Elevated alkaline phosphatase (ALP) is suggestive of local osteolysis
  • Specific tests such as TFTs, cortisol and myeloma screen may be useful
  • Diagnosis
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