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 <or=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 <or=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.