Intact parathyroid hormone measurement 1 hour after thyroid surgery identifies individuals at high risk for the development of symptomatic hypocalcemia

Background

There is currently no consensus regarding the utilization of intact parathyroid hormone (iPTH) for predicting postthyroid surgery hypocalcemia. The objective of this study was to determine a threshold value for the 1-hour postoperative iPTH level that can identify those patients at significantly increased risk for the development of symptomatic hypocalcemia.

Methods

A prospective study of 21 individuals undergoing either total or completion thyroid operations was performed. One-hour postoperative iPTH levels were drawn along with ionized calcium at 6 hours postoperatively and at 7 am the following morning. Symptoms of hypocalcemia were recorded.

Results

Of the 21 patients recruited into the study cohort, there were 18 individuals that developed hypocalcemia (4 symptomatic and 14 asymptomatic) and 3 that remained normocalcemic. The mean iPTH level 1 hour postoperatively was significantly different when comparing the normocalcemic, asymptomatic hypocalcemic, and symptomatic hypocalcemic patient groups (6.50 pmol/L versus 3.76 pmol/L versus 0.7 pmol/L, respectively; P = .007). An iPTH level ≤2.5 pmol/L was 100% sensitive for predicting which individuals would go on to develop symptomatic hypocalcemia.

Conclusions

This study suggests that a 1-hour postoperative iPTH level ≤2.5 pmol/L can identify those individuals at risk for developing symptomatic hypocalcemia. Therefore, we recommend early calcium supplementation for these patients to decrease their postoperative morbidity from symptomatic hypocalcemia.