Association Between Serum Thyrotropin and Cancer Recurrence in Differentiated Thyroid Cancer: A Population-Based Retrospective Cohort Study

Background: Levothyroxine to suppress thyrotropin (TSH) to <0.5 mIU/L following thyroidectomy in differentiated thyroid cancer (DTC) may reduce recurrence in higher-risk DTC. However, there is limited evidence to support guideline recommendations to maintain TSH in the low-normal range of 0.5–2 mIU/L to reduce recurrence in patients with lower risk DTC. The primary objective was to assess the association between exposure to high normal serum TSH (2–4 mIU/L) as compared with low normal TSH (0.5–2 mIU/L) target ranges and cancer recurrence in patients with DTC after thyroidectomy.