Neurodevelopmental Outcome of Infants with Transient Hypothyroxinemia of Prematurity in a Newborn Intensive Care Unit

Objective: The aim of this study was to evaluate neurological development of infants with transient premature hypothyroxinemia (THOP).

Methods: This prospective study included newborns who were born between 28-36 weeks of gestation (GW) and were admitted to the neonatal intensive care unit. Newborns exposed to maternal thyroid disease, or with severe intracranial problems, and congenital anomalies were excluded. Infants with THOP were the study group and those without THOP formed the control group. The study group was subdivided into those receiving levothyroxine replacement (5 μg/kg/day) and those who were untreated. Neonatal demographics, and morbidities, including respiratory distress syndrome, bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) were evaluated. The Ages and Stages Questionnaire (ASQ) and ASQ:Social-Emotional (ASQ:SE) developmental screening tests were administered to the entire study population at the corrected age of two years.

Results: Seventy infants were included in this study, 40 of whom had THOP. The mean GW was 34.4±3.8 weeks in the study group and 37.2±2.3 weeks in controls (p=0.69). Mean overall birth weight was 1640±428 g. Levothyroxine replacement was started in 12/40 infants (30%). The groups were similar in terms of demographic characteristics. Rates of BPD and ROP were higher in the treated group (p=0.01). ASQ and ASQ:SE results did not differ between groups (p=0.75), nor did these scores differ between infants with THOP who did or did not receive levothyroxine (p=0.14).

Conclusion: Although levothyroxine replacement therapy was associated with increased rates of BPD and ROP, this treatment did not appear to improve long-term neurological outcomes in this small group of infants with THOP. Prospective controlled studies with much larger sample sizes are needed to clarify the role of levothyroxine replacement in THOP.