Thyrotropin Level and Thyroid Volume for Prediction of Hypothyroidism Following Hemithyroidectomy in an Asian Patient Cohort

Background As more patients undergo diagnostic thyroid surgery, the development of posthemithyroidectomy hypothyroidism is becoming a major concern. We hypothesized that the preoperative thyrotropin (thyroid-stimulating hormone, TSH) level and ultrasonographically measured thyroid volume, both commonly available in thyroid nodule patients, may predict the development of posthemithyroidectomy hypothyroidism. Method Among the 132 patients who underwent hemithyroidectomy from January 2004 to January 2006, a total of 101 patients who were followed for more than a year were included in the analysis. Results Biochemical hypothyroidism developed in 37 patients (36.6%). Patients who developed postoperative hypothyroidism showed higher TSH levels (P < 0.001) and smaller remnant thyroid volumes (P = 0.014). Logistic regression analysis showed that the TSH level and remnant thyroid volume were independent predictors of posthemithyroidectomy hypothyroidism (P < 0.001 and P = 0.04, respectively). A risk scoring system using these two factors was created based on the results of logistic regression analyses. The incidences of hypothyroidism were 5.3%, 12.1%, 51.7%, and 85.0% according to the risk scores of 0, 1, 2, and 3, respectively. Conclusion Patients with a high preoperative TSH level and small thyroid volume are at high risk of developing hypothyroidism following hemithyroidectomy. Potential risk of postoperative hypothyroidism should be discussed with these patients when thyroid surgery is being considered for a diagnostic purpose.