Hypothyroidism following hemithyroidectomy: Incidence, risk factors, and clinical characteristics

Context: Postoperative thyroid hormone replacement for hypothyroidism following hemithyroidectomy is usually administered without fully understanding the clinical characteristics of the condition. Objective: We aimed to evaluate the clinical characteristics of hypothyroidism following hemithyroidectomy, along with its actual incidence and risk factors. Design, Setting, and Patients: We conducted a retrospective cohort study involving 405 patients undergoing hemithyroidectomy between 2004 and 2011. The mean follow-up duration was 56.4 mo. Intervention: Standardized routine measurement of thyroid function at regular intervals, along with strict criteria for thyroid hormone replacement, was introduced. Main Outcome Measure: The development and clinical course of hypothyroidism following hemithyroidectomy including spontaneous normalization of thyroid function or the need for treatment were evaluated. Results: Hypothyroidism developed in 226 patients (55.8%) after hemithyroidectomy. A preoperative TSH level ≥ 2 mIU/L (odds ratio [OR], 5.517; 95% confidence interval [CI], 3.540-8.598; P < .001), and the coexistence of Hashimoto's thyroiditis (OR, 1.996; 95% CI, 1.107-3.601; P = .022) were found to be independent risk factors for the development of hypothyroidism. Among 222 subclinical hypothyroidism cases, 149 (67.1%) exhibited spontaneous recovery; subgroup analysis of these patients suggested that age ≥ 46 y (OR, 2.395; 95% CI, 1.266-4.533; P = .007) and preoperative TSH level ≥ 2.6 mIU/L (OR, 2.444; 95% CI, 1.330-4.492; P = .004) were independent risk factors for unrecovered subclinical hypothyroidism following hemithyroidectomy. Conclusions: The use of thyroid hormone replacement for subclinical hypothyroidism that develops after hemithyroidectomy should be carefully considered with close followup, while considering the likelihood of the spontaneous return to euthyroidism.