Thyroid Function After Hemithyroidectomy in Children

The risk of hypothyroidism after hemithyroidectomy is not well defined in the pediatric population. We sought to determine the incidence of hypothyroidism after hemithyroidectomy in children and the clinical factors associated with this risk.

This is a retrospective cohort study of consecutive pediatric patients (<19 years of age) who underwent hemithyroidectomy in a pediatric thyroid center between 1998 and 2023, with data available on postoperative thyroid function and/or levothyroxine (LT4) treatment. The primary outcome was the composite of persistent hypothyroidism (thyrotropin [TSH] ≥ 5 mIU/L) or LT4 treatment (PersHypo/LT4). Secondary outcomes were persistent hypothyroidism and transient hypothyroidism. Univariable and multivariable survival analysis and logistic regression were used to evaluate associations of these outcomes with clinical characteristics.

A total of 136 eligible patients (85% female) underwent hemithyroidectomy at a median (range) age of 15.4 (0.14-19.0) years. The median (interquartile range) postsurgical follow-up was 1.10 (0.15-3.2) years for thyroid function and 1.76 (0.38-4.3) years for LT4 treatment status. PersHypo/LT4 occurred in 27/136 patients (20%), with an estimated risk of 18.1% [CI: 12.1-26.6%] at 1 year and 27.5% [CI: 18.7-39.2%] at 5 years. PersHypo/LT4 occurred within 12 months in 21/27 cases (78%) and after 12 months in 6/27 (22%). PersHypo/LT4 was associated with preoperative TSH (hazard ratio 1.89, [CI: 1.31-2.74], p = 0.001), and preoperative TSH ≥ 2 mIU/L optimally distinguished patients with high (58.8%) versus low (12.8%) 5-year risk of PersHypo/LT4 (receiver operator characteristic AUC 0.73, [CI: 0.60-0.85]). The presence of thyroperoxidase (TPO) antibodies was independently associated with increased risk of PersHypo/LT4 (OR: 7.37, [CI: 1.09-49.9], p = 0.041). Persistent hypothyroidism occurred in 14/128 patients (11%), with an estimated 5-year risk of 12.9% [CI: 7.7-21.1%]. Severe hypothyroidism occurred in 5/136 patients (3.7%), and transient hypothyroidism occurred in 22/136 patients (16%).

Persistent hypothyroidism or LT4 treatment occurs in 27.5% of children within 5 years after hemithyroidectomy, usually in the first postoperative year. Preoperative TSH < 2 mIU/L may identify children at low risk, whereas preoperative TSH ≥ 2 mIU/L, particularly in conjunction with TPO antibodies, may identify children at high risk. Transient hypothyroidism also occurs commonly but may not require treatment. These data should inform preoperative counseling and postoperative monitoring around hemithyroidectomy in children.