ESPE Abstracts

Background: Thyroid hormone plays a significant role in development and function of many organ systems especially for brain. Understanding the prevalence of thyroid disorders and characteristic of thyroid function tests in preterm infants are important to diagnosis and provide proper management.

Objectives: The primary objective is to study the prevalence of thyroid disorders in preterm infants. The secondary objectives are to demonstrate the etiology and risk factors of thyroid disorders as well as to study the characteristic of thyroid function tests in preterm infants.

Methods: A retrospective chart review of preterm infants born at tertiary care hospital between 1^st January 2022 and 31^st December 2022 were performed. Preterm infants who had syndromes, congenital anomalies, abnormal chromosome studies, maternal history of thyroid diseases were excluded. Data collection includes demographic data of the preterm infants and their mothers and risk factors which could be associated with thyroid disorders. TSH from newborn screening (NBS) collected by dry blood spot (DBS) and/or thyroid function test (TFT) in 1^st, at 2^nd and after 4^th weeks then every 2 weeks until term. SPSS version 25 was used for statistical analysis.

Results: 603 preterm infant charts were reviewed. The prevalence of thyroid disorders in preterm infants in this study was 18/603 (2.99%) classified to hyperthyrotropinemia 8/18 (44%), hypothyroxinemia of prematurity 4/18 (22%), congenital hypothyroidism 2/18 (11%), transient elevated FT4 2/18 (11%), central hypothyroidism 1/18 (5%) and transient low TSH 1/18 (5%). Statistical analysis by multiple logistic regression shows that maternal preeclampsia in hyperthyrotropinemia preterm infants was 3/8 (37.5%) significantly more than control 73/585 (12.48%) [P = 0.039, OR 5.064, 95%CI (1.084-23.661)]. TSH level increased from 1^st to 2^nd weeks of life in preterm infants GA 28-33 weeks but decrease in preterm infants GA 34-36 weeks. FT4 trends to increase by GA in preterm infants GA less than 34 weeks but decrease in preterm infants GA 34-36 weeks.

Conclusions: The prevalence of thyroid disorders in preterm infants in this study was 3%. The most common cause was hyperthyrotropinemia. Maternal preeclampsia was the risk factor of hyperthyrotropinemia. TSH and FT4 levels were trending up in preterm infants GA less than 34 weeks, which were trending down in preterm infants GA more than 34 weeks.