RESUMO
Objective:To investigate the characteristics of congenital hypothyroidism (CH) in premature infants and analyze the predictors of transient congenital hypothyroidism(TCH) and permanent CH (PCH).Methods:A retrospective study was conducted on the preterm infants with CH born in Beijing from January 2008 to June 2018. They were screened, diagnosed and treated by the Beijing Neonatal Disease Screening Center. They were assigned into TCH and PCH groups according to the clinical prognosis. Univariate analysis and Logistic regression analyses were used to determine the predictors of PCH, and the receiver operating characteristic curve (ROC) was drawn to determine the best cut-off point.Results:A total of 2 216 892 newborns were screened, 15 382 were initially screened positive, the median time of screening was 4(4,10) d after birth, and the median time of postnatal reexamination was 30(22,42) d after birth, 14 576 newborns were reexamined, the reexamination rate was 94.8%. A total of 92 preterm infants were diagnosed with CH, of which 60 were TCH, accounting for 65.2%; 28 were PCH, accounting for 30.4%; and 4 were lost to follow-up, accounting for 4.3%. Univariate analysis showed that in the PCH group, the abnormal rate of thyroid B-ultrasound, levothyroxine (LT4) dose at 1-year old, thyrotropin (TSH) level at 2 years old, LT4 dose at 2 years old, LT4 dose and free thyroxine (FT4) level at 3 years old were higher than those in the TCH group. Logistic regression analysis revealed that abnormal B-ultrasound ( OR=12.184,95% CI 2.270~65.403), and elevated TSH level at 2 years old ( OR=2.033,95% CI 1.280~3.228),increased LT4 dose at 3 year old ( OR=21.435,95% CI 3.439~133.584) are the risk factors for PCH. The maximum area under ROC curve was 0.798 at 3 years old (95% CI 0.680~0.916), the best cut-off point was 1.3 μg/(kg·d) for the 3-year-old drug dose; followed by 2-year-old TSH level, which was 0.683 (95% CI 0.548~0.817), the best cut-off point was 4.51 μIU/ml. Conclusions:TCH accounted for a large proportion of preterm infants with CH. During the follow-up, the increased LT4 dose at 3 years old and the elevated TSH level at 2 years old were the early predictors of PCH.