Postoperative hypoparathyroidism after thyroid surgery

Abstract

Postoperative hypocalcaemia, secondary to hypoparathyroidism, is the most common complication observed in patients who undergo bilateral thyroid resection. Although hypocalcaemia is self-limiting in most patients and does not require treatment, symptomatic hypocalcaemia is of particular concern. The cause of postoperative hypoparathyroidism has commonly been attributed to devascularization and injury to the parathyroid glands or their accidental resection. Depending on the extent of parathyroid gland devascularization, hypocalcaemia may be transient, resolving in a few months, or it may be permanent, requiring lifelong oral calcium and vitamin D supplementation. The degree of functional reduction of the parathyroid parenchyma seems to be directly related to the degree of severity of postoperative hypocalcaemia and to the earlier onset of postoperative hypocalcaemic symptoms. Early postoperative monitoring of serum calcium concentration has been demonstrated to be useful in the identification of patients in whom postoperative hypocalcaemia will develop. However, even though the serum calcium slope may correlate with the development of symptomatic hypocalcemia, these results are often not useful until 12 or 24 hours after the operation. This delay can postpone therapy and prolong hospitalization. On the other hand, many studies have demonstrated the usefulness of perioperative parathormone measurement in the identification of patients who are at risk of develo** hypoparathyroidism and symptomatic hypocalcaemia. These studies demonstrated that absolute levels or percentage decline of PTH measured minutes to hours after thyroidectomy accurately predict postoperative serum calcium levels and can identify patients at risk of postoperative hypocalcaemia who require supplementation treatment, and those not at risk who can be safely discharged without any supplementation treatment. Moreover, combining postoperative PTH and serum calcium levels could result in an accurate prediction of the risk of postoperative hypocalcaemia.