THYROID HORMONE REPLACEMENT AFTER THYROID LOBECTOMY

Background—The purpose of this study was to determine the incidence of and identify risk factors for post-operative hypothyroidism in patients undergoing thyroid lobectomy. Methods—We 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. Results—In this study, 14.3 % of patients developed hypothyroidism and required thyroid hormone supplementation. These hypothyroid patients had a higher mean pre-operative TSH and lower mean free T4 serum levels compared to euthyroid patients (TSH: 2.12 vs. 1.35 µIU/ml, P=0.006; free T4: 1.03 vs. 1.34 ng/dl, P=0.01, respectively). When stratified into three groups based on their pre-operative 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<0.001). In addition, patients with Hashimoto’s thyroiditis were significantly more likely to become hypothyroid (OR 3.78, 95 % CI 2.17 – 6.60). Conclusion—Following thyroid lobectomy, approximately 1 in 7 patients will experience hypothyroidism requiring thyroid hormone treatment. Patients with pre-operative 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