Hypocalcemia is a well-described complication associated with total thyroidectomies. We investigated the role of early intraoperative parathyroid hormone (PTH) measurement and relative differences in PTH in predicting those patients at risk of postoperative hypocalcemia.
This was a retrospective study. Inclusion criteria were all patients undergoing completion/total thyroidectomy from March 2016 to March 2017 under a single surgeon. All patients had PTH assay performed at induction of anesthesia and intraoperatively (IOPTH) following thyroid excision. The differences in mean between preoperative vs. intraoperative PTH were assessed using a Wilcoxon rank-sum test. Relationships between PTH and ∆PTH with postoperative calcium levels were assessed using Pearson’s correlation and a binomial regression analysis was also performed.
The cohort comprised 25 female and three male patients. The mean IOPTH level was significantly lower than the preoperative levels (18.6 ± 19.4 vs. 52.11 ± 46.3; two-tailed p <0.0001). The mean postoperative calcium level was significantly lower than the preoperative calcium level (2.22 ± 0.2 mmol/l vs. 2.29 ± 0.16 mmol/l, respectively, p = 0.162). Attempted correlation of IOPTH levels with postoperative calcium yielded a Pearson’s correlation coefficient R of 0.064 (p = 0.748). A weakly negative correlation was found between ∆PTH and postoperative calcium, R = −0.216. Binomial logistic regression analysis was not statistically significant for this cohort (X2 = 10.8; p = 0.216).
We found no association between PTH levels and postoperative calcium levels. ∆PTH may be a superior parameter in predicting postoperative hypocalcemia in total thyroidectomy. Post hoc analysis of existing study databases could further demonstrate the advantage of ∆PTH in risk stratification.