Supplementary Material for: Early Discontinuation of Levothyroxine Treatment Is Safe and Feasible in Extremely Low Birth Weight Infants with Delayed Hyperthyrotropinemia

<b><i>Background:</i></b> While recent pieces of evidence suggest that discontinuation of levothyroxine replacement therapy (LRT) earlier than the current guidelines of 3 years is possible, the optimal duration of LRT for delayed hyperthyrotropinemia in extremely low birth weight infants (ELBWIs) remains unknown. <b><i>Objective:</i></b> This study aimed to investigate the feasibility of early discontinuation of LRT for delayed hyperthyrotropinemia in ELBWIs. <b><i>Methods:</i></b> The medical records of 92 ELBWIs who had shown delayed hyperthyrotropinemia, defined as a delayed rise in thyroid-stimulating hormone (TSH) levels to &gt;20 µIU/mL after initial normal TSH level, were retrospectively reviewed to determine whether the duration of LRT affects the short-term outcomes at discharge from neonatal intensive care unit (NICU) and the long-term outcomes at the corrected age (CA) of 2 years. The infants were grouped into: no LRT required group (<i>n</i> = 21), short-term LRT given until the time of NICU discharge – 90 ± 64 (13–211) days group (<i>n</i> = 36), and long-term LRT given – 749 ± 333 (339–1,967) days group (<i>n</i> = 35). <b><i>Results:</i></b> While mortality in the no LRT required group was significantly higher than that in the long-term LRT group, no significant differences were observed in short-term outcomes at discharge from NICU and long-term growth and neurodevelopmental outcomes at CA of 2 years between the short- and long-term LRT groups. <b><i>Conclusions:</i></b> Termination of LRT at around the time of discharge from NICU in well, clinically stable ELBWIs who have delayed hyperthyrotropinemia appears to be safe and feasible and avoids the risk of overtreatment.

背景：尽管近期研究证据表明，左甲状腺素替代治疗（levothyroxine replacement therapy, LRT）可在早于当前3年指南的时间内停药，但针对极低出生体重儿（extremely low birth weight infants, ELBWIs）迟发性促甲状腺素血症的最优LRT疗程仍不明确。
目的：本研究旨在探究极低出生体重儿迟发性促甲状腺素血症早期停用左甲状腺素替代治疗的可行性。
方法：对92例确诊为迟发性促甲状腺素血症的极低出生体重儿的临床病历进行回顾性分析，该病症定义为初始促甲状腺素（thyroid-stimulating hormone, TSH）水平正常后，该指标延迟升高至＞20 µIU/mL，旨在明确LRT疗程对新生儿重症监护病房（neonatal intensive care unit, NICU）出院时的短期结局，以及校正胎龄（corrected age, CA）2岁时的长期结局的影响。将受试婴儿分为三组：无需LRT组（n=21）、短期LRT组（于NICU出院时停药，疗程为90±64天，范围13~211天，n=36）、长期LRT组（疗程为749±333天，范围339~1967天，n=35）。
结果：无需LRT组的死亡率显著高于长期LRT组，但短期LRT组与长期LRT组在NICU出院时的短期结局，以及校正胎龄2岁时的长期生长与神经发育结局方面均无显著差异。
结论：对于临床状态稳定、确诊迟发性促甲状腺素血症的极低出生体重儿，在其NICU出院前后停用左甲状腺素替代治疗似乎安全可行，可避免过度治疗的风险。