BACKGROUND
Thyroid cancer is usually initially treated by surgery. This can either be a lobectomy (removal only the thyroid lobe containing the cancer) or a total thyroidectomy (removal of the entire thyroid). Many thyroid cancers are low risk (small, confined to the thyroid gland and no evidence for spread to the outside the thyroid to the lymph nodes in the neck) and many patients have do fine after only a lobectomy. One advantage of a thyroid lobectomy is the possibility the patient will maintain normal thyroid function from the remaining lobe and will not need lifelong thyroid hormone therapy via medications. However, many of the studies indicating patients will not need thyroid hormone after lobectomy included patients who did not have thyroid cancer. This is an important distinction as one of the goals after thyroid surgery for thyroid cancer is often to keep the TSH level in the low normal range. Thus, after a lobectomy for thyroid cancer, thyroid hormone therapy may be indicated even if the TSH level is in the normal range. This study was performed to see how often patients who had a lobectomy for low-risk thyroid cancer needed thyroid hormone after the surgery and why the treatment was started.

THE FULL ARTICLE TITLE
Schumm MA et al. 2021 Frequency of thyroid hormone replacement after lobectomy for differentiated thyroid cancer.

SUMMARY OF THE STUDY
This was a study of patients taken care of at one medical center who had a thyroid lobectomy and a low-risk thyroid cancer removed with that surgery.

Patients who were already on thyroid hormone before surgery or started on thyroid hormone before the first TSH test, those that were pregnant or had another tiny thyroid cancer not related to the primary nodule/cancer for which the surgery was performed were not included in the study.

A total of 115 patients were included in the study and 70% were women. The average age was 50 years old and 73% had a TSH level before surgery of <2 (the upper cut off TSH desired for patients with active or a history of thyroid cancer). Patient charts were followed for an average of 2.6 years.

A total of 84% of patients had a TSH >2 after surgery, which was an average of 39 days after surgery. Compared to patients with a postoperative serum TSH >2 mIU/L, patients with a serum TSH ≤2 mIU/L were younger, had lower TSH levels before surgery, and were more likely to have cancers ≥1 cm. Overall, 68% of patients with a TSH >2 after surgery were started on thyroid hormone.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
The majority of patients who had a thyroid lobectomy for low-risk thyroid cancer had a post-operative TSH >2 and most of those patients were started on thyroid hormone. This is important to patients because they should be aware that it is likely they will need at least a small dose of thyroid hormone after thyroid lobectomy as the remaining thyroid lobe will likely not make enough thyroid hormone to maintain a TSH level <2.

— Joshua Klopper, MD

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