Thyroid-stimulating hormone reference ranges for moderate-to-late preterm infants.

BACKGROUND Identifying congenital hypothyroidism through newborn screening (NBS) is higher among moderate-to-late preterm (MLPT) infants. Currently, the same thyroid-stimulating hormone (TSH) cutoffs are used for term and preterm infants. TSH reference ranges for MLPT infants are not currently available. OBJECTIVE To determine TSH reference ranges for MLPT infants. METHODS We analyzed 10,987 TSH levels on NBS samples performed on 8499 MLPT infants born between 32 and 36 weeks gestation. RESULTS TSH median, 5th, 25th, 75th, 95th, and 99th percentiles were defined from day 1 until day 14 of life. TSH levels gradually decreased after birth and reached a plateau around day 6. CONCLUSION Using a state-wide cohort, we constructed TSH reference charts from day 1 until day 14 for MLPT infants. Relationship between age-adjusted TSH percentiles and long-term neurodevelopmental outcomes should be determined in future studies to define optimal TSH cutoffs for MLPT infants.