Higher preablative serum thyroid-stimulating hormone level predicts radioiodine ablation effectiveness in patients with differentiated thyroid carcinoma.

Introduction Radioiodine ablation of remnant thyroid tissue is an important adjuvant therapy of differentiated thyroid carcinoma (DTC) after thyroidectomy. Elevated serum thyroid-stimulating hormone (TSH) level is necessary for successful ablation. The optimum level of serum TSH level necessary for successful radioiodine ablation of well-DTC is, however, yet to be defined. We aimed to determine whether higher serum TSH level will result in a better rate of complete ablation of well-DTC using iodine-131 (131I) following initial thyroidectomy. Patients and methods A total of 109 patients with differentiated thyroid cancer were divided into four treatment groups on the basis of serum TSH levels. They were followed up from 6 to 12 months after treatment with stimulated serum thyroglobulin level and a diagnostic whole-body scan with radioactive iodine 131I to determine early response. Results Sixty-four patients had papillary thyroid carcinoma, whereas 45 patients had follicular carcinoma. An excellent response was observed in 66.7% of patients with TSH level more than 90 μIU/ml, 72.2% in the group with TSH level of 60–89 μIU/ml, 48.5% when TSH was 30–59 μIU/ml and 26.7% when TSH was less than 30 μIU/ml (P=0.002). Conclusion Higher preablative serum TSH predicts a better rate of ablation in patients with differentiated thyroid cancer treated with 131I after thyroidectomy.