Development of a tool to calculate the probability of hypocalcemia after total thyroidectomy: a prospective study

Purpose This study aimed to evaluate the ability of the percentage of decrease in serum PTH level in the first 8 h after total thyroidectomy (TT) to predict hypocalcemia requiring Ca supplementation and develop a tool to predict it. Methods 97 patients who underwent TT with measurement of preoperative parathyroid hormone (PTH) levels were prospectively evaluated 1 and 8 h after TT; postoperative magnesium (Mg2PO) and phosphorus levels were evaluated on the 2nd day after surgery. The percentage of decrease in PTH level 1 h (%dPTH1h) and 8 h (%dPTH8h) postoperatively and predictors of hypocalcemia requiring Ca supplementation were evaluated and an equation was developed to predict this outcome. Results %dPTH1h ( p = 0.002), %dPTH8h ( p = 0.001) and (Mg2PO) ( p < 0.01) were isolated predictors of postoperative hypocalcemia requiring Ca supplementation. The data obtained led to the development of two tools to predict this complication. Conclusions The percentage of decrease in PTH level 1 h and 8 h postoperatively and the magnesium level on the 2nd day after surgery were predictors of more severe hypocalcemia, and an auxiliary tool for predicting this complication was developed.