Parathyroid hormone: a sensitive predictor of hypocalcemia following total thyroidectomy

To investigate whether monitoring parathyroid hormone (PTH) could predict hypocalcemia following total thyroidectomy or other bilateral thyroid manipulations.

Forty patients undergoing total thyroidectomy as well as other bilateral thyroid procedures were prospectively enrolled. PTH levels were measured preoperatively and 30 minutes postoperatively. Calcium levels were measured preoperatively and every 8-12 hours for the first 72 postoperative hours. Changes in PTH levels as well as symptoms of hypocalcemia were correlated with postoperative hypocalcemia.

Hypocalcemia developed in 13/40 patients (32.5%), mainly those patients undergoing total thyroidectomy in conjunction with paratracheal neck dissections. The respective sensitivity and specificity of a drop in PTH for detecting hypocalcemia was 92% and 66% (50% drop), 23% and 75% (75% drop), and 46% and 100% (drop below normal range).

A 50% drop in PTH levels 30 minutes following bilateral thyroid procedures is a sensitive predictor of hypocalcemia. A drop of 75% is a highly specific indicator of postoperative hypocalcemia, though not highly sensitive.

C-4.