Hypothyroidism Following Hemithyroidectomy: Incidence, Risk Factors, and Clinical Characteristics

Postoperative thyroid hormone replacement for hypothyroidism following hemithyroidectomy is usually administered without fully understanding the clinical characteristics of the condition. We aimed to evaluate the clinical characteristics of hypothyroidism following hemithyroidectomy, along with its actual incidence and risk factors. We conducted a retrospective cohort study involving 405 patients undergoing hemithyroidectomy between 2004 and 2011. The mean follow-up duration was 56.4 mo. Standardized routine measurement of thyroid function at regular intervals, along with strict criteria for thyroid hormone replacement, was introduced. The development and clinical course of hypothyroidism following hemithyroidectomy including spontaneous normalization of thyroid function or the need for treatment were evaluated. 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. 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.