Hypocalcaemia

Acute severe hypocalcaemia most often occurs following extensive neck surgery e.g. for thyroid cancer. This emergency guide outlines a strategy to prevent this complication and to treat it and other causes of severe hypocalcaemia.

 

Has the patient undergone previous neck surgery of any form?  

Any neck surgery can lead to hypoparathyroidism, which is most commonly transient but can be permanent in up to 1% all neck surgeries.

This is most commonly seen following extensive surgery for thyroid cancer, or other head and neck malignancy, but can also complicate surgery for benign thyroid disease, hyperparathyroidism, laryngeal or oesophageal pathology.

Transient post-surgical HPTH usually recovers within 6-12 months, and can be predicted by PTH levels >18ng/l.

Surgery for hyperparathyroidism may also lead to the hungry bone syndrome. After chronic hypercalcaemia, the dramatic fall in PTH leads to marked skeletal calcium uptake and the patient may become hypocalcaemic requiring high dose calcium replacement for several days post operatively.

Is the patient at high risk of vitamin D deficiency?

Patients who habitually stay out of the sun, cover their skin, or are residents of care homes are at particularly high risk of vitamin D deficiency. 

Is the patient known to have hypoparathyroidism (HPTH), a family history of this or another rare endocrine conditions?

The index of suspicion for severe hypocalaceamia is significantly increased in patients known to have HPTH, a family history of HPTH or other complex condition e.g. Wilson's disease.

Does the patient complain of tingling, numbness or paraesthesia around the mouth, hands or feet?

Perioral paraesthesia and cramps are the commonest symptoms of hypocalcaemia of any cause.

Does the patient complain of muscle cramps, twitching or difficulty breathing?  

Muscle cramps and sometimes spontaneous contractions are common symptoms of hypocalcaemia of any cause.

Severe cramp or carpopedal spasm indicates more severe hypocalcaemia.

Laryngospasma nd bronchospasm are rare but can occur with severe hypocalceamia.

Has the patient ever presented with confusion or seizures?

This usually occurs only in very severe untreated hypocalcaemia, and so usually precedes diagnosis of HPTH.

Has the patient experienced any collapses, palpitations or known bradyarrhythmias?

Cardiac conduction disturbance usually ony occurs with severe hypocalcaemia.

What medication does the patient take?  

HPTH has also been associated with chemotherapeutic agents and antiretroviral drugs, but is most commonly seen with proton pump inhibitors through hypomagnesaemia.

Is the patient undernourished, alcoholic, or have any other potential cause of hypomagnesaemia e.g. severe burns or malabsorption?  

Any cause of hypomagnesaemia may lead to reduced production of PTH and hence hypocalcaemia due to HPTH.

Hypomagnesaemia may also occur with renal tubular defects. Very rarely, hypomagnesaemia may occur due to HNF1 mutations which more commonly cause maturity onset diabetes of the young (MODY).

Is the patient presenting in the neonatal period?

Transient HPTH may occur in offspring of mothers with hyperparathyroidism, in premature or very low birth wieght babies. Hypomagensaemia in diabetic mothers may also lead to transient neonatal HPTH.