Does the Risk of Hypocalcemia Increase in Complementary Thyroidectomy Performed in Papillary Thyroid Cancer?

Objectives: Papillary thyroid cancer (PTC) is the most common type of thyroid cancers. In some patients, due to the histopatho-logical features of PTC, complementary thyroidectomy (CT) may be needed to contralateral thyroid lobe after lobectomy. Hypo-calcemia is the most common complication after thyroidectomy and its etiology is multifactorial. It is still controversial whether the CT increases the risk of hypocalcemia or not. In this study, we aimed to evaluate whether CT procedure increases the risk of hypocalcemia compared to total thyroidectomy (TT) in PTC patients.Methods: The data of the patients who were operated between 2015 and 2018 and diagnosed with PTC in the pre-operative or post-operative period were evaluated retrospectively, and two patient groups were formed. Group 1 included 19 patients who were diagnosed with PTC in the pathological examination after lobectomy was performed in the first operation, and after that CT was performed to the contralateral lobe. Among the patients who were diagnosed with pre-operative or post-operative PTC in the same period, 53 patients with characteristics similar to the 1st group in terms of age and gender were selected for Group 2. Biochemical parameters related to calcium metabolism in the pre-operative and post-operative periods, parathyroid autotransplantation and un-intentional parathyroid gland removal, post-operative hypocalcemia, and treatment rates were compared between the two groups. Results:There were 19 patients (13 F and 6 M) with a mean age of 48.3 +/- 12.1 years and 53 patients with a mean age of 46.3 +/- 9 (40 F and 13 M) in Groups 1 and 2, respectively, and there was no significant difference between the groups in terms of age and gender. There was no significant difference in terms of pre-operative parathormone (PTH), phosphorus (P), magnesium (Mg), Vitamin D deficiency rate, parathyroid autotransplantation, and presence of parathyroid gland in thyroid specimen. Pre-operative calcium (Ca) value was 9.33 +/- 0.46 in Group 1 and lower than Group 2 (9.65 +/- 0.41) (p=0.012). There was no significant difference between the groups in terms of post-operative day 0 Ca, P, Mg, and PTH and post-operative day 1 Ca, Mg, and PTH. Post-operative day 1 P level was significantly lower in Group 1 (2.86 +/- 0.72) compared to Group 2 (3.6 +/- 0.83). Post-operative hypocalcemia rates were 21.1% and 30.2% in Groups 1 and 2, respectively, and the difference was not significant (p=0.558). In both groups, hypocalcemia was transient and permanent hypoparathyroidism was not detected. Parathyroid autotransplantation rates (10.5% vs. 3.8%; p=0.283) and the rate of unintentionally removed parathyroid gland (0 vs. 15.1; p=0.185) were similar in Groups 1 and 2, respectively. Ca and active Vitamin D administration rates in the post-operative period were similar in Group 1 and Group 2 (10.5% vs. 22.6%; respectively), and there was no significant difference between the groups in terms of receiving treatment (p=0.327).Conclusion: CT can be necessary in some patients with post-operative diagnose of PTC. CT can be performed without increased risk of hypocalcemia compared to TT.