Thyroid hormone replacement after thyroid lobectomy

BackgroundThe purpose of this study was to determine the incidence of and identify risk factors for postoperative hypothyroidism in patients undergoing thyroid lobectomy.MethodsWe retrospectively reviewed patients who underwent a thyroid lobectomy for benign disease from May 2004 to December 2007. Patients with known hypothyroidism or on preoperative thyroid hormone replacement were excluded.ResultsIn this study, 14.3% of patients developed hypothyroidism and required thyroid hormone supplementation. These hypothyroid patients had a higher mean pre-operative thyroid-stimulating hormone (TSH) and lower mean free thyroxine (T4) serum levels compared with euthyroid patients (TSH, 2.12 vs 1.35 μIU/mL [P = .006]; free T4, 1.03 vs 1.34 ng/dL [P = .01]). When stratified into 3 groups based on their preoperative TSH measurement (≤1.5, 1.51–2.5, and ≥2.51 μIU/mL), the rate of hypothyroidism increased significantly at each level (13.5%, 20.5%, and 41.3%, respectively [P < .001]). In addition, patients with Hashimoto's thyroiditis were significantly more likely to become hypothyroid (odds ratio, 3.78; 95% confidence interval, 2.17–6.60).ConclusionAfter thyroid lobectomy, approximately 1 in 7 patients experience hypothyroidism requiring thyroid hormone treatment. Patients with preoperative TSH levels >1.5 μIU/mL, lower free T4 levels, and Hashimoto's thyroiditis are at increased risk and should be counseled and followed appropriately.