BACKGROUND
Surgery is an option to treat thyroid cancer as well as enlarged thyroid glands that cause symptoms such as difficulty swallowing, pressure on the neck or bulging in the neck. When the enlargement/abnormality/cancer is limited to one lobe, a lobectomy can be performed, leaving most of the rest of the thyroid intact. One of the reasons to remove only the lobe is to decrease the risk of developing hypothyroidism after surgery. Currently, hypothyroidism requiring thyroid hormone therapy following lobectomy may occur in 8 to 50% of cases. There is an increased likelihood of hypothyroidism after lobectomy in patients with elevated thyroid stimulating hormone (TSH) levels before surgery, positive thyroid peroxidase antibodies, thyroid cancer as the reason for the surgery, and small thyroid tissue left behind. This study was performed to determine the frequency of hypothyroidism and timing of beginning thyroid hormone therapy after lobectomy over a 15-year follow-up period.

THE FULL ARTICLE TITLE
Barranco H et al 2023 Thyroid hormone replacement following lobectomy: Long-term institutional analysis 15 years after surgery. Surgery 173:189–192.

SUMMARY OF THE STUDY
This study identified patients who underwent thyroid lobectomy, for any indication, at a single institution between 2005 and 2010. Studied patients had no prior thyroid surgery, prior or subsequent radioactive iodine therapy, or need for thyroid hormone before surgery. The primary outcome was initiation of thyroid hormone therapy in patients with TSH levels >4.5 mIU/L. The timing of thyroid hormone therapy initiation during the 10- to 15-year follow-up period was determined using provider notes, medication data, and/or direct telephone contact.

The study included 235 patients, 96.6% of whom had a benign pathology. Thyroid hormone therapy was started in 46.8% of patients. The average timing of thyroid hormone therapy initiation was 1.7 years after lobectomy, with 25% starting therapy 2 years after surgery. By 5 years after lobectomy, thyroid hormone therapy had been started in 89% of patients. Additional data in 45% of patients requiring thyroid hormone therapy demonstrated an average TSH level after surgery of ~9 mIU/L prior to starting thyroid hormone therapy. Of those with a benign pathology, 46.3% required thyroid hormone therapy. Compared with the patients who did not require thyroid hormone therapy, patients who required thyroid hormone therapy were more likely to have concurrent Hashimoto’s thyroiditis. Age, sex, surgical indication, and cancer rates were similar between the thyroid hormone therapy and non- thyroid hormone therapy groups.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study showed that thyroid hormone replacement therapy is started in 46.3% of patients after lobectomy for benign disease. Further, 25% do not start therapy until 2 years after surgery. Accordingly, the authors suggest that thyroid function testing should occur annually for a minimum of 2 years after lobectomy.

— Alan P. Farwell, MD

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