Prediction of Thyroid Hormone Replacement Following Thyroid Lobectomy: A Long-term Retrospective Study

OBJECTIVE: Following thyroid lobectomy, patients are at risk for hypothyroidism. This study sought to determine the incidence of postlobectomy thyroid hormone replacement as well as predictive risk factors to better counsel patients. STUDY DESIGN: Retrospective cohort study. SETTING: Patients aged 18 to 75 years treated in a single academic institution who underwent thyroid lobectomy from October 2006 to September 2017. METHODS: Patients were followed for an average of 73 months. Demographic data, body mass index, size of removed and remnant lobe, preoperative thyroid-stimulating hormone (TSH) level, final thyroid pathology, and presence of thyroiditis were collected and analyzed. Risk factors were evaluated with chi-square analyses, t tests, logistic regression, and Kaplan-Meier analysis. RESULTS: Of the 478 patients reviewed, 369 were included in the analysis, 30% of whom eventually required thyroid hormone replacement. More than 39% started therapy >12 months postoperatively, with 90% treated within 36 months. Patient age ≥50 years and preoperative TSH ≥2.5 mIU/L were associated with odds ratios of 2.034 and 3.827, respectively, for thyroid hormone replacement. Malignancy on final pathology demonstrated an odds ratio of 7.76 for hormone replacement. Sex, body mass index, volume of resected and remaining lobes, and weight of resected lobe were not significant predictors. CONCLUSION: Nearly a third of patients may ultimately require thyroid hormone replacement. Age at the time of surgery, preoperative TSH, and final pathology are strong, clinically relevant predictors of the need for future thyroid hormone replacement. After lobectomy, patients should have long-term thyroid function follow-up to monitor for delayed hypothyroidism.