Introduction.

Hypocalcemia after total thyroidectomy is a common complication in thyroid surgery. Parathyroid hormone has been shown to be a reliable predictor for detecting patients with at high risk of significant hypocalcemia and the consequent need for calcium supplementation. The objective of this study was to determine the optimal time for measuring parathormone for this purpose.

Methods.

Prospective study carried out in two level 3 institutions in Popayán, Colombia, between April 2016 and February 2018, in which levels of preoperative parathormone were measured at 0, 2, 4 and 12 hours postoperatively, and compared with the values ​​obtained at 3 months of follow-up in patients undergoing total thyroidectomy. A parathormone value less than 10 pg/ml or a decrease greater than 80% with respect to the pre-surgical value was considered as risk groups and in need of calcium supplementation.

Results.

Thirty-four operated patients were included. Taking as a threshold a value of less than 10 pg/ml, the measurement of parathormone at 4 hours was sensitive and specific (60% and 93.1%, respectively). For a decrease greater than 80% with respect to the presurgical value, the sensitivity was 60% and the specificity was 96.5%, presenting a positive predictive value of 75% and a negative predictive value of 93.3% (p <0.001).

Discussion.

A decrease of more than 80% in the preoperative parathyroid hormone value measured at 4 hours after total thyroidectomy allows the identification of those patients at high risk of significant hypocalcaemia, who require early administration of calcium supplements, compared with the determination of the decrease at 0, 2 and 12 hours postoperatively.

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