Hypoparathyroidism

Hypoparathyroidism is characterised by low levels of PTH. It is most commonly caused by accidental injury to the glands during thyroid surgery. The second most common cause is autoimmune destruction. Hypoparathyroidism causes hypocalcaemia.

Postsurgical hypoparathyroidism can occur after thyroid, parathyroid, or radical neck surgery for head and neck cancer. It may be transient, intermittent, or permanent. Transient hypoparathyroidism occurs in up to 20% of cases. Because of the high risk for hypoparathyroidism, calcium levels should be monitored after thyroid surgery.

Clinical features

Manifestations depend on the severity and rate of development of the hypocalcaemia.

The most common acute manifestation is tetany (numbness, cramps, laryngospasm, seizures, etc.). Chronic hypoparathyroidism causes calcification of basal ganglia which leads to extrapyramidal symptoms, as well as skeletal abnormalities, cataracts, and abnormal skin.

Diagnosis and evaluation

Labs show hypocalcaemia, low or normal PTH, and hyperphosphataemia. Signs of hypocalcaemia, including Chvostek sign and Trousseau sign, may be present.

If there is no history of neck surgery, the underlying cause should be sought.

Treatment

In case of acute, severe hypocalcaemia, IV calcium must be supplemented. In other cases, oral supplements of calcium and vitamin D are sufficient. Recombinant PTH exists and may be used, but it’s expensive, administered subcutaneously, and long-term safety is unknown.