Prospective, Five-Year Evaluation of Thyroid Function Following Thyroid Lobectomy

Introduction: Postoperative hypothyroidism following thyroid lobectomy has been reported in 5-50% of patients. Many studies reporting these data have been retrospective with relatively short follow up. The aim of this study is to prospectively evaluate for post-operative development of hypothyroidism following thyroid lobectomy. This will allow for improved patient education and counseling, as avoidance of postoperative hypothyroidism is one advantage cited by many surgeons advocating for lobectomy rather than total thyroidectomy.

Methods: These results represent an interim analysis of an ongoing prospective study. Adult patients undergoing thyroid lobectomy at a single academic center were recruited and monitored for postoperative hypothyroidism. Thyroid stimulating hormone (TSH) levels were collected at 6 weeks, 3 months, 6 months, 12 months, 18 months, and annually from years 2 - 5. Initiation of thyroid hormone replacement, starting dose and dose trajectory was also collected. Multiple logistic regression was used to evaluate risks factors for postoperative hypothyroidism, including age, gender, resected thyroid volume, remaining thyroid volume, co-existent thyroiditis and co-existent malignancy.

Results: In total, 67 patients have been enrolled in the study to date, 55% of which were female with average age of 41. The most common diagnosis was adenomatoid nodule, followed by papillary thyroid carcinoma. Of the total patients, 22% were started on levothyroxine for elevated TSH. The most common starting dose was 50mcg, with doses ranging from 25mcg to 137mcg. The first abnormal TSH typically presented within the first 6 months, with the most common first occurrence being at 6 weeks postoperatively (53%). No significant association identified with previously reported risks factors.

Conclusions: Our prospective analysis shows 22% of patients were started on thyroid supplementation for elevated TSH, with 50mcg being the most common dose. Continuation of our prospective evaluation is needed to confirm these results and further identify potential risk factors associated with postoperative hypothyroidism.