A Comparison of Postnatal Factors between Infants with a Delayed TSH Rise on the Newborn Screen and those with a Timely Diagnosis of Congenital Hypothyroidism

The purpose of this study was to identify postnatal factors that may confer an increased risk for having a delayed thyroid-stimulating hormone (TSH) rise on the newborn screen (NBS) in infants admitted to the neonatal intensive care unit (NICU).

NBS results were collected from the Indiana State Department of Health (ISDH) for all cases of congenital hypothyroidism (CH) from 2012 to 2022 and used to identify infants who had a delayed TSH rise (N = 73). Thirty-six infants with a delayed diagnosis were matched by gestational age and birth weight Z-scores to infants with CH who were diagnosed in a timely manner per their initial NBS. A retrospective chart review was performed to compare postnatal factors between these two groups and to determine the treatment outcome in infants with a delayed versus timely diagnosis of CH.

Infants with a delayed TSH rise had significantly higher odds of medication exposures, invasive surgical procedures, and complications related to the renal, gastrointestinal, and hematologic systems. Delayed infants had 3.02 times the number of bedside procedures that involved iodine-containing sterile preparation (95% confidence interval [CI]: 1.31-6.93, p = 0.009) compared with the timely cohort. Within the delayed cohort, 38% of infants were found to have transient CH as compared with 27% of infants in the timely cohort.

Several postnatal factors appear to play a role in conferring a risk for a delayed TSH rise, implying that the etiology of this phenomenon is multifactorial. Our findings suggest the need for more targeted screening for CH within the NICU.

· The delayed cohort had a higher likelihood of medication exposure and multiorgan system complications.. · The delayed cohort had a greater degree of iodine exposure than the timely cohort.. · More than a third of infants in the delayed cohort were found to have transient CH..