Single measurement of intact parathyroid hormone after thyroidectomy can predict transient and permanent hypoparathyroidism: a prospective study

Abstract

Objective: Immediate postoperative hypocalcemia is the most common complication of bilateral thyroidectomy. Although hypocalcemia is usually transient, it can be fatal. This study aimed to find a predictor of immediate postoperative hypocalcemia by using intact parathyroid hormone (PTH) level at 4 hours after thyroidectomy (iPTH4hr) compared with the decline in the percentage of intact PTH (%iPTH). We also followed the subjects for evaluation of permanent hypoparathyroidism.

Methods: This was a prospective study of 65 patients (86.2% female, mean age: 43±15 years) who planned to undergo total or subtotal thyroidectomy. Preoperative and iPTH4hr were measured.

Results: Thirty-nine patients (60%) were diagnosed with papillary thyroid carcinoma, while the rest were multinodular goiter (21.5%) and Graves' disease (7.7%). Significant immediate hypocalcemia was observed in 25 (38.5%) patients. Both iPTH4hr <12.5 pg/mL and %iPTH decline >72% could accurately predict significant immediate hypocalcemia. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for iPTH4hr were 92%, 87.5%, 82.1%, and 94.6%, respectively. The %iPTH decline was equal in accuracy, with sensitivity, specificity, PPV, and NPV of 84%, 90%, 84%, and 90%, respectively. At 6 months after surgery, 19 patients (29.2%) displayed permanent hypoparathyroidism. The iPTH4hr <12.5 pg/mL and %iPTH decline >72% could also predict permanent hypoparathyroidism, with sensitivity, specificity, PPV, and NPV of 100%, 80.4%, 67.9%, and 100%, and 94.7%, 84.8%, 72%, and 97.5%, respectively.

Conclusions: Only a single measurement of iPTH4hr could be helpful in identifying patients at risk of significant immediate hypocalcemia in need prompt treatment, and subsequently facilitating early discharge of patients. Also, this parameter can precisely predict permanent hypoparathyroidism.

Keywords: Hypocalcemia; Hypoparathyroidism; Parathyroid hormone; Thyroidectomy; Vitamin D.