Postoperative hypoparathyroidism after total thyroidectomy for thyroid cancer

Postoperative hypoparathyroidism (HPT) is one of the most common complications in total thyroidectomy for thyroid carcinoma. Parathyroid glands (PTGs) are at risk of being damaged during total thyroidectomy and central neck dissection mainly due to inadvertent removal, interruption of the blood supply or hematoma formation. The purpose of this study was to evaluate the efficacy of our surgical procedure to preserve for parathyroid function retrospectively and to clarify the risk factors of HPT after total thyroidectomy for thyroid cancer.

Sixty-five patients undergoing total thyroidectomy with central neck dissection for thyroid cancer were enrolled in this retrospective study. Cancers were diagnosed as stage I in 15 patients, stage II in 24 patients, stage III in 19 patients, and stage IV in 7 patients. Lateral neck dissection and upper mediastinal dissection were simultaneously performed in 47 patients and one patient, respectively. Parathyroid glands (PTGs) were preserved in situ in 34 patients. Among 31 patients in whom PTG could not be preserved in situ, two or more PTGs were autotransplanted in 9 patients and one PTG was autotransplanted in 18 patients. PTG was not autotransplanted in 4 patients, since it could not be identified during the surgery.

Postoperative transient HPT and permanent HPT were observed in 44 (68%) patients and in 12 (18%) patients, respectively. Among 34 patients in whom PTGs were preserved in situ, transient HPT and permanent HPT were observed in 17 (50%) patients and in 6 (2%) patients, respectively. Among 31 patients in whom PTG were not preserved in situ, postoperative permanent HPT was observed in all 4 patients without PTG autotransplantation, and 6 (33%) out of the 18 patients who had one PTG autotransplantation. On the other hand, none of the 9 patients who had two or more PTG autotransplantation at the time of thyroidectomy developed permanent HPT (P=0.04). The patients with large tumor (≥40mm) and/or gross extra glandular invasion had a significantly higher risk of permanent postoperative HPT compared with the patients without these pathological features (P<0.01).

Two or more PTG should be autotransplanted in case where PTG is not preserved in situ to prevent postoperative HPT after total thyroidectomy with central neck dissection, especially in cases of large tumor and/or gross extrathyroidal extension.