Effect of Isthmus-preserving Thyroid Lobectomy on Postoperative L-thyroxine Requirement

Background and Objective: L-thyroxine requirement is an unintended consequence after thyroid lobectomy, but it occurs frequently. This study aims to investigate the effect of isthmus-preserving lobectomy to avoid L-thyroxine supplementation. Methods: Retrospectively, we studied on 125 patients (29 men, 96 women, male-to-female ratio: 1/3:3, mean age: 43.9) who had undergone lobectomy for various indications and who were enrolled between September 2019 and February 2023. Among these patients, 77 underwent isthmus-removing (IR) lobectomy, while 48 underwent isthmus-preserving (IP) lobectomy. Thyroid function tests and thyroid antibodies were monitored preoperatively and postoperatively at 1, 3, and 6 months. L-thyroxine was administered to patients who developed hypothyroidism according to blood thyrotropin hormone (TSH) level. Results: In the IR group, 32 (41.6%) cases, while in the IP group, 11 (22.9%) cases needed to use L-thyroxine. In a univariate analysis, isthmus removal ( P = 0.035), a higher preoperative TSH level ( P = 0.009), and higher antithyroid peroxidase antibody (anti-TPO) level ( P = 0.011) were identified as significant factors associated with postoperative L-thyroxine requirement. However, multivariate analysis revealed that isthmus removal is the sole factor leading to the requirement of L-thyroxine ( P = 0.021). Conclusion: Isthmus-preserving lobectomy seems to be effective in preventing postoperative L-thyroxine usage in cases without thyroiditis. On the other hand, high preoperative TSH and anti-TPO levels increase the need for L-thyroxine usage after surgery.