BACKGROUND
Surgery to remove all, or part, of the thyroid gland is usually needed when thyroid cancer is discovered. Sometimes, removing only that part, or side, of the thyroid gland that contains cancer (a thyroid lobectomy) is enough to treat this disease. This is especially true for papillary thyroid cancers that have a very low risk of growing and spreading. The main advantage of a thyroid lobectomy is that the remaining thyroid lobe may make enough thyroid hormone to avoid needing thyroid hormone treatment following surgery, as often, but not always, this remaining thyroid tissue will make enough thyroid hormone to meet a person’s needs. While a total thyroidectomy affords the lowest risk of thyroid cancer recurrence, it requires life-long treatment with thyroid hormone after surgery.

It would be useful to know, before surgery, if the noncancerous side of the thyroid gland will produce enough thyroid hormone after surgery to avoid taking a thyroid hormone pill. If this is the case, a person might choose to just have the cancer-containing side of their thyroid removed. The research described here aims to identify features of people diagnosed with thyroid cancer that predict adequate thyroid hormone production when only one side of the thyroid is removed.

THE FULL ARTICLE TITLE
Dou Y et al 2021 The recovery of thyroid function in low-risk papillary thyroid cancer after lobectomy: A 3-year follow-up study. Front Endocrinol (Lausanne) 11:619841. PMID: 33633689.

SUMMARY OF THE STUDY
The authors of this study looked at 190 people who underwent a thyroid lobectomy for treatment of thyroid cancer. The investigators then asked which of these people had low enough thyroid hormone levels to need treatment with a thyroid hormone pill.

Those people in the study who did require thyroid hormone replacement were then further evaluated to try and understand if there was anything about them that might have predicted, before surgery, that they would need a thyroid hormone pill following thyroid lobectomy. The authors found that 113 people in the study (47%) had normal thyroid hormone levels after thyroid lobectomy, while 28 people developed temporary low thyroid hormone levels that returned to normal 3-9 months after surgery. Overall, 49 of 190 (26%) of patients were found to have permanent low thyroid hormone levels after surgery and needed long-term treatment with thyroid hormone pills. The authors found no relationship between the need for thyroid hormone treatment after thyroid lobectomy and gender, age, cancer size, cancer location within the thyroid or body mass index. The authors did find that people who had thyroid hormone levels at the lower end of normal before surgery were more likely to need to take thyroid hormone after thyroid lobectomy. They also found that inflammation of the thyroid (Hashimoto’s thyroiditis) before surgery was associated with need for thyroid hormone after thyroid lobectomy. Further, and for unclear reasons, thyroid hormone was more likely to be needed if the right side of the thyroid was removed, compared to the left.

WHAT ARE THE IMPLICATIONS OF THIS STUDY?
This study shows that only ~25% of thyroid cancer patients require thyroid hormone pills after a lobectomy. Another 15% that had low thyroid hormone levels after surgery eventually regained normal thyroid hormone levels within 3-9 months. Predictors of the need for thyroid hormone after a lobectomy include pre-op thyroid levels in the low normal range, the presence of Hashimoto’s thyroiditis and a need for a right-sided lobectomy. These findings may help some thyroid cancer patients choose between thyroid surgery options.

— Jason D. Prescott, MD PhD

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