Newborn Screening for Delayed TSH Rise and Atypical Congenital Hypothyroidism

A new study investigated thyroid function abnormalities and associated conditions in very preterm (VPT) or very low birth weight (VLBW) infants.

This retrospective review was conducted on neonates admitted to UC Irvine Medical Center from 2012-2020. All newborns underwent repeat thyroid screening at one month of age. Those with abnormal thyroid-stimulating hormone (TSH) or free thyroxine levels underwent further testing and endocrinology consultation. 

It was noted that among the 430 infants included, 14.9% had elevated TSH, and 4.8% had low free thyroxine. Risk factors for delayed TSH rise included being small for gestational age, patent ductus arteriosus, and late-onset sepsis. Six infants (1.4%) were diagnosed with atypical congenital hypothyroidism, requiring treatment until discharge. However, none of these cases were identified by newborn screening. 

Percentile cutoffs for TSH at one month of age were suggested to enhance screening sensitivity. Repeat thyroid screening is recommended in VPT or VLBW infants to detect atypical congenital hypothyroidism that may require intervention.

Thyroid dysfunction manifesting as low FT4 or elevated TSH at 1 month of life is relatively common in infants born very preterm and/or infants with VLBW. Those neonates, including some with atypical congenital hypothyroidism requiring thyroxine therapy, are at risk of being missed by newborn screening. Rescreening with a single TSH measurement using a cutoff of 7.2 μIU/mL in infants with ELBW (90th percentile for this population) and 6.1 μIU/mL in infants with a birth weight of 1000-1500g (95th percentile for this population) at first month after birth may provide a reasonable repeat screening strategy. 

Source: Nolan B, Uy C, Stablein L, Bany-Mohammed F. The Journal of Pediatrics. 2024 Jun 1;269:113974.