Higher Incidence Rates of Hypothyroidism and Late TSH Rise in Preterm Very-Low-Birth-Weight Infants at a Tertiary Care Center

Background/aims: Preterm newborns with a very low birth weight (VLBW) of < 1,500 g have an atypical form of hypothyroidism with a delayed rise in TSH, necessitating a second newborn screening specimen collection. The aims of this study were to survey the compliance with second newborn screening to detect delayed TSH rise in VLBW preterm infants at a tertiary care center, and to determine the rate of atypical hypothyroidism.

Methods: Retrospective review of the records of 104 preterm VLBW infants. Late TSH rise was defined as an increase in TSH concentration after 14 days of age in the presence of a normal initial screen.

Results: The compliance rate was 92% for the second screening. High rates of hypothyroidism (16.3%) and of late TSH rise (4.8%) were detected. Patients with hypothyroidism had a significantly lower birth weight (p = 0.01) and longer hospital stay (p = 0.004). Patients with late versus those with early TSH rise had a significantly lower mean birth weight (851 ± 302 vs. 1,191 ± 121 g, p = 0.004).

Conclusion: The rates of early and late TSH rise in this VLBW population were higher than those in the literature and could be due to the use of povidone-iodine disinfectants. The yield of a second TSH screening in this study was high indicating the need for vigilance in screening VLBW preterm infants.