Endocrine Abstracts

Introduction: Patients undergoing parathyroidectomy routinely stay in hospital overnight if they have primary hyperparathyroidism or longer if they have secondary hyperparathyroidism due to the risk of postoperative hypocalcaemia. There is no reliable way of predicting whether the often observed transient mild hypocalcaemia will progress, necessitating treatment. Frequent serum calcium checks remain the only way to ensure that hypocalcaemia does not go untreated. Prescribing calcium and Vitamin D supplements for all patients would over treat a significant proportion of patients.

Objective: The objective was to establish whether intra and perioperative PTH levels could predict the occurrence of postoperative hypocalcaemia in patients undergoing parathyroidectomy for either primary or secondary hyperparathyroidism.

Methods: The study was carried out prospectively from January 2005 to March 2006. All patients undergoing parathyroidectomy within this period were eligible. Venous blood samples were taken preoperatively, post-induction, post-mobilisation of the gland(s), 5 minutes post-excision, 10 minutes post-excision, 6 hours postoperatively and 20 hours postoperatively and analyzed for serum calcium and PTH levels. The end point of interest was biochemical hypocalcaemia (corrected calcium <2.20 mmol/L) within 48 hours of operation.

Results: 45 patients undergoing parathyroidectomy for either primary (32 patients) or secondary (13 patients) hyperparathyroidism were identified. 1 patient (3%) with primary hyperparathyroidism became hypocalcaemic secondary to severe acute pancreatitis. 9 patients (69%) with secondary hyperparathyroidism became hypocalcaemic. The proportion of patients with secondary hyperparathyroidism who became hypocalcaemic was statistically significantly different (P<0.0001) compared to primary hyperparathyroidism. In patients with secondary hyperparathyroidism, there was no significant difference in mean PTH levels at any time point when comparing those who did develop hypocalcaemia with those who did not.

Conclusions: Perioperative PTH levels are not useful in predicting postoperative hypocalcaemia following parathyroidectomy. Patients with secondary hyperparathyroidism are at high risk of developing hypocalcaemia whereas patients with primary hyperparathyroidism rarely develop this condition.