Intact parathyroid hormone measurement at 24 hours after thyroid surgery as predictor of parathyroid function at long term

Background

There is no consensus about the usefulness of postoperative intact parathyroid hormone (iPTH) determination to predict permanent hypoparathyroidism (pHPP). We evaluated the value of calcium (Ca²⁺) and iPTH concentration at 24 hours after total thyroidectomy (TT) for predicting pHPP.

Methods

Ca²⁺ and iPTH levels from 70 consecutive patients who underwent TT were measured at 24 hours and 6 months after TT.

Results

Five patients (7.1%) developed pHPP. An iPTH concentration ≤5.8 pg/mL at 24 hours after TT identified patients at risk for pHPP (sensitivity, 100%; specificity, 81.5%), but it was not accurate enough to predict its development (positive predictive value, 30%). Conversely, an iPTH level >5.8 pg/mL predicted normal parathyroid function at 6 months (negative predictive value, 100%). Compared with iPTH, a postoperative Ca²⁺ level ≤1.95 mmol/L was 60% sensitive and 78.5% specific to predict pHPP.

Conclusions

An iPTH concentration >5.8 pg/mL on the first postoperative day rules out pHPP with much better diagnostic accuracy than Ca²⁺. Postoperative iPTH could be helpful in identifying patients at risk for developing pHPP.