Development of delayed thyroid stimulating hormone elevation in small-for-gestational-age infants: is a second screening needed?

Purpose: Recent reports indicate that small for gestational age (SGA) could be a risk factor for delayed thyroid stimulating hormone (dTSH) elevation in preterm infants. The development of dTSH elevation in SGA late-preterm infants with a gestational age of 34-36 weeks has been investigated in only a few studies. Methods: In the present retrospective study, 70 SGA infants and 86 sex- and gestational age-matched controls who presented with normal results on initial thyroid function testing were included. Results: SGA infants had a significantly higher prevalence of dTSH elevation (15.7% vs. 3.5%, P=0.009) compared with appropriate-for-gestational age infants. In SGA infants, the mean age at the time of dTSH was 24 days. Development of dTSH was associated with SGA and medical treatment with dopamine or furosemide. After adjusting for confounding factors, multiple logistic regression analysis showed SGA was a significant risk factor for the development of dTSH elevation (odds ratio, 23.2; 95% confidence interval, 2.27-236.91; P=0.008). Conclusion: SGA infants may be at risk for dTSH and clinicians could consider a second thyroid screening test around the age of 1 month.