Hypocalcemia after thyroidectomy: iPTH levels and iPTH decline are predictive? Retrospective cohort study

Background: Hypocalcemia is the most common complication of thyroid surgery. The aim of this study was to determine the early predictive factors of postoperative hypocalcemia and to analyze their efficiency. Methods: We performed a retrospective study of 345 consecutive patients who underwent total thyroidectomy at the Endocrine Surgery Department (Policlinico G. Rodolico Hospital of Catania) between January 2011 and November 2013. We measured serum intact parathormone (iPTH) levels preoperatively and 4 h after surgery. The threshold values of hypocalcemia for iPTH levels and iPTH relative decline were obtained by receiver operating curves (ROC) analysis. Results: The incidence of hypocalcemia was 32.2% (111 of 345 patients). Our statistical analysis revealed that hypocalcemia rate was strongly correlated with the lower iPTH values and greater iPTH decline (P < 0.001). The threshold enabling prediction of hypocalcemia were 12,5 pg/mL for iPTH and 55,7% for relative iPTH decline. Patients with iPTH<12,5 pg/mL developed hypocalcemia in 58.6% of cases while those with iPTH ≥12,5 pg/dl in 18.8%. Among 175 patients with iPTH relative decline greater than 55,7% hypocalcemia was diagnosed in 91 cases (52%), while other 170 patients with iPTH relative decline less than 55,7% developed hypocalcemia only in 20 cases (11,7%). Conclusions: The decreased iPTH levels and increased iPTH relative decline resulted to be an accurate predictive factors of postoperative hypocalcemia. The early administration of Calcium and vitamin D in the high-risk patients should be put on in order to prevent the symptoms of hypocalcemia and to reduce the costs and duration of hospitalization.