Identification of secondary predictive factors for acute hypocalcemia following thyroidectomy in patients with low postoperative parathyroid hormone levels without overt calcium deficiency: A cohort study

Background The transient acute hypocalcemia (HypoCa) is the most prevalent complication after total thyroidectomy, detected primarily by subnormal intact parathyroid hormone (iPTH) and calcium levels. However, the need for calcium supplementation is ambiguous in patients who exhibit low iPTH with normal calcium levels. The aim of this study was to evaluate complementary predictors of HypoCa in this scenario. Methods A retrospective cohort study with of 1597 consecutive patients undergoing total thyroidectomy, with or without neck dissection, from January 2014 to December 2018 at a single institution. Patients with an iPTH <12 pg/mL and a total calcium level ≥8 mg/dL in the first 8 h after surgery were included. Results 1597 patients identified with low postoperative iPTH without overt calcium deficiency was diagnosed. The transient HypoCa in that specific subgroup was 509 (31.9%). Multivariate analysis indicated that HYPOCA was associated with bilateral level VI neck dissection and pre- to postoperative calcium reduction >38 pg/mL. To better illustrate the model, we plotted a nomogram with the variables selected for the final model. Conclusion Total thyroidectomy patients who exhibit low postoperative iPTH levels without overt calcium deficiency should be considered for calcium replacement therapy when they a marked drop in iPTH postoperatively and underwent bilateral level VI neck dissection.