One-Hour Postoperative Parathyroid Hormone Levels Do Not Reliably Predict Hypocalcemia After Thyroidectomy

Area of Science:

• Endocrinology
• Surgical Complications
• Oncology

Background:

• Hypocalcemia is a common complication following total thyroidectomy.
• Low postoperative parathyroid hormone (PTH) levels have been suggested as a predictor of hypocalcemia.
• Definitive study designs to confirm PTH's predictive value are lacking.

Purpose of the Study:

• To determine if postoperative PTH levels alone can accurately predict biochemical hypocalcemia after total thyroidectomy.
• To evaluate the accuracy of different PTH thresholds in predicting hypocalcemia.

Main Methods:

• A prospective study included 218 patients undergoing total or completion thyroidectomy.
• Biochemical hypocalcemia was defined as ionized calcium <1.13 mmol/L or serum calcium <8.4 mg/dL.
• Three PTH thresholds were examined: <10 pg/mL, <20 pg/mL, and >50% drop from baseline at 1 hour postoperatively.

Main Results:

• PTH <10 pg/mL showed 36.5% sensitivity and 89.2% specificity.
• PTH <20 pg/mL had 66.4% sensitivity and 67.6% specificity.
• A >50% PTH drop had 63.4% sensitivity and 72.5% specificity. False-negative rates ranged from 33.6% to 63.5%, and false-positive rates from 10.8% to 32.4%.

Conclusions:

• Postoperative PTH levels are unreliable for predicting hypocalcemia after total thyroidectomy.
• Current PTH thresholds result in high rates of false negatives and false positives.
• Further prospective studies are necessary to establish the true utility of PTH in post-thyroidectomy management.