Objective: To determine the frequency of levothyroxine (LT4) supplementation after therapeutic lobectomy for low-risk differentiated thyroid cancer (DTC).
Methods: This retrospective cohort study enrolled adult patients with low-risk DTC confirmed using surgical pathology who underwent therapeutic lobectomy at a single institution from January 2016 through May 2020. The outcome measures were postoperative serum thyroid-stimulating hormone (TSH) levels and the initiation of LT4. The predictors of a postoperative TSH level of >2 mU/L and initiation of LT4 were evaluated using Cox proportional hazards models.
Results: Postoperative TSH levels were available for 115 patients (91%), of whom 97 (84%) had TSH levels >2 mU/L after thyroid lobectomy. Over a median follow-up of 2.6 years, a postoperative TSH level of >2 mU/L was associated with older age (median 52 vs 37 years; P = .01), higher preoperative TSH level (1.7 vs 0.85 mU/L; P < .001), and primary tumor size of <1 cm (38% vs 11%, P = .03). Multivariate analysis revealed that only preoperative TSH level was an independent predictor of a postoperative TSH level of >2 mU/L (hazard ratio [HR] 1.53, P = .003). Among patients with a postoperative TSH level of >2 mU/L, 66 (68%) were started on LT4 at a median of 74 days (interquartile range 41-126) after lobectomy, with 51 (77%) undergoing at least 1 subsequent dose adjustment to maintain compliance with current guidelines.
Conclusion: More than 80% of the patients who underwent therapeutic lobectomy for DTC developed TSH levels that were elevated beyond the recommended range, and most of these patients were prescribed LT4 soon after the surgery.
Keywords: levothyroxine; low-risk DTC; thyroid hormone supplementation; thyroid lobectomy.
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