Abstract: Background：There are few reports about the outcomes of neonatal hyperthyrotropin (HT) in China. Objective：To investigate the outcome and influencing factors of HT in neonatal intensive care units (NICU). Design：Case-control study. Methods：Consecutive cases of HT infants were enrolled in the NICU of Xinjiang Uygur Autonomous Region People's Hospital from January 1, 2011, to December 31, 2021. The inclusion criteria were as follows: the concentration of thyroid-stimulating hormone (TSH) was 6-20 mU·L^-1at the first test between 3 and 21 days after birth and the free thyroxine (FT4) was within the normal range. During the follow-up after discharge, TSH<6 mU·L^-1 was considered as the normal level and TSH≥10 mU·L^-1 was the indicator for levothyroxine (LT4) as needed. A dosage less than 3 μg·kg^-1·d^-1 could be an indicator for considering discontinuation of LT4 treatment. The administration could be stopped if TSH was tested normal in the re-examination 1 month later. Main outcome measures：The influencing factors of abnormal TSH levels at 3 months of age (90±15 days) and LT4 treatment discontinuation at the age of 3 years. Results：A total of 836 neonates were included in this study. At 3 months of age, 390 cases were lost to followup or unable to be assessed. Normal thyroid function was found in 304 cases ［TSH: 3.6 (2.7,4.5) mU·L-1, FT4:18.3 (15.6,20.4) pmol·L^-1］, and thyroid dysfunction was found in 142 cases［TSH: 17.7 (9.6,22.1) mU·L^-1, FT4 is 15.7 (13.3,19.4) pmol·L-1］. The influencing factors of thyroid dysfunction were female (OR=1.68, 95%CI: 1.07-2.64), cesarean section (OR=0.52, 95%CI: 0.32-0.83), maternal thyroid disease during pregnancy (OR=0.31, 95%CI: 0.15-0.67), comorbid congenital malformation or syndrome (OR=7.92, 95%CI: 2.22-28.25), infectious disease at admission (OR=0.56, 95%CI: 0.33-0.96). At the age of 3 years, among 142 children with thyroid dysfunction, 18 (12.6%) were lost to follow-up, 48 (33.8%) turned into normal TSH levels without taking LT4, and 45 out of 76 cases taking LT4 stopped the administration and 31 still continued the treatment. The risk of not being able to discontinue LT4 treatment before the age of 3 years was 4.89 times higher in infants with congenital malformations or syndromes compared to those without the comorbidity (OR=4.89, 95% CI: 1.06-22.57). Conclusion：Special attention should be paid to the follow-up of thyroid function in HT infants in the NICU, especially for female infants and those with comorbid congenital malformations or syndromes.

Key words: Hyperthyrotropinemia, Outcomes, Therapy, Follow-up