Risk Factors of Hypothyroidism after Hemithyroidectomy

Abstract

Background : Some patients who were euthyroid before hemithyroidectomy for thyroid tumor develop postoperative hypothyroidism. They must receive regular outpatient treatment and take L-thyroxine all their life. If we were able to predict residual thyroid function after hemithyroidectomy preoperatively, this would help us explain to patients their probability of developing postoperative hypothyroidism. Patients and Methods : To evaluate risk factors of postoperative hypothyroidism after hemithyroidectomy, we retrospectively reviewed 170 euthyroid (preoperative serum TSH and Free T4 level were within the reference values) patients. The patients were divided into three groups according to postoperative thyroid function, i.e. a normal group, elevated TSH group (Free T4 level was normal), and decreased Free T4 group. We then analyzed the risk factors which influenced the postoperative thyroid function. Results and Conclusion : We did not find any significant differences among the three groups with respect to age, gender, histological evaluation (malignant or benign) or anti-TPO/Tg antibodies. However, we found that postoperative hypothyroidism significantly correlated with the preoperative serum TSH and Free T4 levels. Our results suggest that 90% of patients whose serum TSH level is under 2.0 μU/ml will be euthyroid after surgery, and 71% of patients whose preoperative serum TSH level is over 2.0 μU/ml and serum Free T4 level is under 1.0 ng/dl will need thyroid hormone replacement therapy.