Effect of (131)I ‘clear residual thyroid tissue’ after surgery on the function of parathyroid gland in differentiated thyroid cancer

Thyroid cancer is a common malignant tumor of the endocrine glands. Although surgery is the optimal treatment utilized, the disease is characterized by recurrence and metastasis. The aim of the present study was to determine the effect of iodine-131 ((131)I) ‘clear residual thyroid tissue’ following surgery on the treatment of differentiated thyroid cancer (DTC) and its effect on the function of the parathyroid gland. A total of 160 patients diagnosed with DTC, who were consecutively admitted to our Hospital between June 2012 and June 2014 and underwent total thyroidectomy or subtotal resection, were included in the present study. After three months, the patients were administered (131)I ‘clear residual thyroid tissue’ treatment and underwent a whole body scan after 1 week to determine whether ‘clear residual thyroid tissue’ treatment was successful or not. The treatment was repeated within 3 months if not successful. Of the 160 patients, 24 patients had cancer metastasis (15.0%). The average dose of (131)I used for the first time was 6.4+1.2 GBq and the treatment was successful in 66 cases (41.3%). The average treatment time was 2.8±0.6 therapy sessions. The results showed that, prior to and following the first treatment and at the end of the follow up, levels of the parathyroid hormone, serum calcium and phosphorus were compared, and no statistically significant difference (P>0.05) was observed. There were 5 patients with persistent hypothyroidism and 8 patients with transient hypothyroidism. The levels of thyroglobulin were significantly decreased, and the difference was statistically significant (P<0.05). A total of 48 patients (30%) with hypothyroidism were identified. In conclusion, the results have shown that DTC resection and (131)I ‘clear residual thyroid tissue’ treatment did not significantly impair the parathyroid function, thereby improving the treatment effect.