A single parathyroid hormone measurement two hours after a thyroidectomy reliably predicts permanent hypoparathyroidism.
INTRODUCTION
Hypoparathyroidism is the most common complication following thyroidectomy, and various algorithms for early detection have been suggested. The aim of this study was to evaluate the predictive value of measuring the parathyroid hormone level 2 h after thyroidectomy and whether determination of the perioperative decline in parathyroid hormone added diagnostic value.


METHODS
Patients subjected to thyroidectomy for benign thyroid disorders were analyzed in (1) a retrospective register-based study (366 consecutive patients treated during 2015-2016) and (2) a prospective observational study (39 patients treated during 2018). Optimal cut-off values for postoperative parathyroid hormone and perioperative decline (%) in parathyroid hormone were determined by receiver operating characteristics and area under the curve. Sensitivity, specificity, positive and negative predictive values were calculated using cross tabulation.


RESULTS
The prevalence of hypoparathyroidism the first day after thyroidectomy was higher among patients treated for hyperthyroidism (30% vs 20%; P = 0.03). The optimal cut-off level for postoperative parathyroid hormone was 1.1 pmol/L (area under the curve = 0.887, 95% confidence interval: 0.839-0.934; positive predictive value: 88%, negative predictive value: 93%) for the entire cohort. When the groups were analyzed separately, the optimal cut-off was 1.05 for the non-hyperfunctioning group and 1.55 pmol/L for the group with hyperthyroidism. Twelve months after thyroidectomy, 3% were defined as having permanent hypoparathyroidism. Measurement of parathyroid hormone decline added diagnostic value for one patient with preoperative parathyroid-hormone-elevation associated with vitamin D deficiency.


CONCLUSIONS
For patients with vitamin D sufficiency, the diagnostic accuracy of a single measurement of parathyroid hormone 2 h after thyroidectomy is an excellent indicator for predicting transient hypoparathyroidism.
['Palmhag|David|D|', 'Brydolf|Jacob|J|', 'Zedenius|Jan|J|', 'Bränström|Robert|R|', 'Nilsson|Inga-Lena|IL|https://orcid.org/0000-0002-8966-3729']
parathyroid hormone Thyroidectomy hypoparathyroidism hypocalcemia