Developmental Trends in Postnatal Thyroid Hormones and Thyroid Dysfunction in Preterm Infants Born at less than 34 weeks Gestation.

Objectives: To analyse the trends in thyroid function tests (TFT) in preterm infants, evaluate the frequency of thyroid dysfunction, and identify the factors that influence thyroid function.

Methods: The TFT results and risk factors for thyroid dysfunction in preterm infants with gestational ages (GA) between 25 and 34 weeks were analysed.

Results: In total, 535 infants were enrolled in this study. Thyroid hormone levels vary with gestational and postnatal age, and the total frequency of thyroid dysfunction is 50.3%. Thirty-one infants (5.8%) had delayed TSH elevation. Transient hypothyroxinaemia of prematurity remained significantly associated with both lower birth weight and GA. Congenital hypothyroidism was significantly associated with lower birth weight, 5 min Apgar score, and dopamine use.

Conclusions: Thyroid hormone levels in preterm infants are related to gestation and postnatal age, the frequency of thyroid dysfunction in premature infants is high, and is negatively correlated with GA and birth weight.