A single parathyroid hormone level obtained 4 hours after total thyroidectomy predicts the need for postoperative calcium supplementation.

Background: Parathyroid hormone (PTH) levels after total thyroidectomy have been shown to predict the development of symptomatic hypocalcemia and the need for calcium supplementation. This study aimed to determine whether a PTH level drawn 4 hours postoperatively is as effective as a level drawn on postoperative day 1 (POD1) in predicting this need.

Study Design: This is a single-institution retrospective review of 4-hour and POD1 PTH levels in patients who underwent total thyroidectomy from January 2012 to September 2012. If POD1 PTH was ≥10 pg/mL, patients did not routinely receive supplementation; if PTH was <10 pg/mL, patients received oral calcium with or without calcitriol.

Results: Of 77 patients, 20 (26%) had a 4-hour PTH <10 pg/mL; 18 (90%) of these patients had a POD1 PTH <10 pg/mL. No patient with a 4-hour PTH ≥10 pg/mL had a POD1 PTH <10 pg/mL. All 18 patients with POD1 PTH <10 pg/mL received calcium supplementation. Three additional patients received supplementation due to reported symptoms or surgeon preference. A 4-hour PTH ≥10 pg/mL compared with a POD1 PTH had a similar ability to predict which patients would not need calcium supplementation; sensitivity was 98% vs 98%, specificity was 90% vs 86%, and and negative predictive value was 95% vs 95%. Of 21 patients who received supplementation, 13 (62%) also received calcitriol, including 9 patients (69%) with a 4-hour PTH <6 pg/mL.

Conclusions: A single PTH level obtained 4 hours after total thyroidectomy that is ≥10 pg/mL accurately identifies patients who do not need calcium supplementation or additional monitoring of serum calcium levels. Same-day discharge, if deemed safe, can be accomplished with or without calcium supplementation based on the 4-hour PTH level. Greater consideration should be given to calcitriol supplementation in patients with a 4-hour PTH <6 pg/mL.