Thyroidectomy and parathyroid hormone: tracing hypocalcemia-prone patients

Background The aim of this prospective study was to identify patients at high risk of developing hypocalcemia after thyroidectomy on the basis of the parathyroid hormone (PTH) level on the first postoperative day. Methods We included 160 patients undergoing total thyroidectomy in a period of 6 months by the same surgical team in this study. In all patients the PTH level was measured before surgery on the day of surgery (PTH1), and on the first postoperative day (PTH2), whereas serum calcium level was measured daily until discharge. Patients were classified as hypocalcemic if they had a serum calcium level less than the normal range on the first postoperative day, independently of symptoms of hypocalcemia. Results At an average follow-up period of 5.9 months (range, 4–9 mo), 66 patients were considered hypocalcemic, 57 patients (35.6%) had a transient hypocalcemia, and 9 patients (5.6%) required calcium–vitamin D supplementation for persistent hypocalcemia. The mean PTH1 value was 54.4 ± 17.2 pg/mL (median, 53.85 pg/mL), the mean PTH2 value was 22.8 ± 13.3 pg/mL (median, 21 pg/mL). The mean PTH decrease in value was 51.54% ± 27.4% (median, 51.83%; range, 4%–94%) and 43.7% of patients presented a PTH decrease of more than 50%. The presence of a postoperative hypocalcemia was statistical correlated both with the PTH2 level and with the PTH drop percent value (P < .001 and P = .002, respectively). With the use of the receiver operating characteristic curve, the maximum sum of the sensitivity and specificity for the correlation of PTH2 levels and hypocalcemia occurred at a PTH2 level of 9.6 pg/mL. Conclusions The PTH measurement on the first postoperative day may be considered a useful method to predict postthyroidectomy hypocalcemia, thus avoiding prolonged hospitalization. Moreover, PTH dosage at first postoperative day is more reliable and less expensive than intraoperative quick PTH assay.