Association Between Thyroid Gland Volume and Postoperative Hypothyroidism Following Hemithyroidectomy

Objective To evaluate whether the proportion of resected thyroid tissue or the residual lobe volume predicts postoperative hypothyroidism following hemithyroidectomy. Study Design Multicenter retrospective cohort study. Setting Ziv Medical Center and Galilee Medical Center, Israel. Methods The study included 134 adult patients who underwent hemithyroidectomy between 2017 and 2024. Patients with preexisting hypothyroidism or malignant histopathology were excluded. Preoperative thyroid gland volumes were measured by computed tomography (CT) and correlated with serum thyroid hormone profiles (T3, T4, and TSH) obtained preoperatively, and at 1 and 6 months postoperatively. Associations between thyroid volume parameters and postoperative hypothyroidism were analyzed statistically. Results Postoperative hypothyroidism developed in 29.1% of patients, within the first postoperative month. Affected patients exhibited significantly higher baseline TSH levels than euthyroid counterparts (3.0 vs 1.4 μIU/mL, P < .001). No significant correlation was found between postoperative thyroid function and total gland volume, resected lobe volume, or residual‐to‐total volume ratio. At 6 months, only 12% of patients remained hypothyroid, suggesting partial recovery of thyroid function in the remaining lobe. Conclusion Neither the extent of resection nor the residual thyroid volume predicted postoperative hypothyroidism. These findings imply that factors beyond gland size—such as preoperative functional reserve or intrinsic thyroid health—may play a more decisive role in maintaining postoperative endocrine stability. Identifying these predictors could enhance patient selection, risk stratification, and postoperative follow‐up.