Frequency of Thyroid Hormone Replacement after Lobectomy for Differentiated Thyroid Cancer

Abstract: Objective To determine the frequency of levothyroxine (LT4) supplementation after therapeutic lobectomy for low-risk differentiated thyroid cancer (DTC). Methods Retrospective cohort study of adult patients with low-risk DTC confirmed on surgical pathology who underwent therapeutic lobectomy at a single institution from January 2016 through May 2020. Outcome measures were postoperative serum TSH levels and the initiation of LT4. Predictors of post-operative TSH >2 mIU/L and initiation of LT4 were evaluated using Cox proportional hazards models. Results Postoperative TSH levels were available in 115 (91%) patients, of whom 97 (84%) had TSH levels > 2 mU/L after thyroid lobectomy. Over a median follow up of 2.6 years, postoperative TSH> 2 was associated with older age (median 52 vs. 37 years; p=0.01), higher preoperative TSH (1.7 vs. 0.85 mU/L; p 2 mU/L (HR 1.53, p=0.003). Among patients with postoperative TSH >2 mU/L, 66 (68%) were started on LT4 at a median (interquartile range) of 74 [41-126] days after lobectomy, with 51 (77%) experiencing at least one subsequent dose adjustment to maintain compliance with current guidelines. Conclusions More than 80% of patients who underwent therapeutic lobectomy for DTC developed TSH levels that were elevated beyond the recommended range, and most of these patients were prescribed LT4 soon after surgery.